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Difference between revisions of "2010 AMC 10B Problems"

(→‎Problem 7)
Line 1: Line 1:
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4. For a real number x, define #(x) to be the average of x and x^2. What is #(1)+#(2)+#(3)?
 
−
(A)3 (B)6 (C)10 (D)12 (E)20
 
  
−
5. A month with 31 days has the same number of Mondays and Wednesdays. How many of the seven days of the week could be the first day of this month?
 
−
(A)2 (B)3 (C)4 (D)5 (E)6
 
−
 
−
6.A circle is centered at O, AB is a diameter and C is a point on the circle with angle COB=50 (degrees). What is the degree measure of CAB?
 
−
(A)20 (B)25 (C)45 (D)50 (E)65
 
−
 
−
7.A triangle has side lengths 10, 10, and 12. A rectangle has width 4 and area equal to the area of the triangle. What is the perimeter of this triangle?
 
−
(A)16 (B)24 (C)28(D)32 (E)36
 
−
 
−
8. A ticket to a school play costs x dollars, where x is a whole number. A group of 9th graders buys tickets costing a total of <math>48, and a group of 10th graders buys tickets costing a total of </math>64. How many values for x are possible?
 
−
(A)1 (B)2 (C)3 (D)4 (E)5
 
−
 
−
9.Lucky Larry's teacher asked him to substitute numbers for a, b, c, d, and e in the expression a-(b-(c-(d+c))) and evaluate the result. Larry ignored the parenthesis but added and subtracted correctly and obtained the correct result by coincidence. The numbers Larry substituted for a,b,c, and d were 1,2,3, and 4, respectively. What number did Larry substitute for e?
 
−
(A)-5 (B)-3 (C)0 (D)3 (E)5
 
−
 
−
10.Shelby drives her scooter at a speed of 30 miles per hour when it is not raining, and 20 miles per hour when it is raining. Today she drove in the sun in the morning and in the rain in the evening, for a total of 16 miles in 40 minutes. How many minutes did she drive in the rain?
 
−
(A)18 (B)21 (C)24 (D) 27(E)30
 
−
 
−
11. A shopper plans to purchase an item that has a listed price greater than 100 dollars and can use any one of three coupons. Coupon A gives 15 percent of the listed price, B gives 30 dollars of the listed price, and C gives 25 percent of the amount by which the listed price exceeds 100 dollars.
 
−
Let x and y by the smallest and largest prices, respectively, for which Coupon A saves at least as many dollars as B or C. What is y-x?
 
−
(A)50 (B)60 (C)75 (D80 (E)100
 
−
 
−
12.At the beginning of the school year, 50 percent of all students in Mr. Well's class answered "yes" to the question "Do you like math?" and 50 percent answered "No". At the end of the school year, 70 percent answered "yes" and 30 percent answered "No". Altogether, x% of the students gave a different answer at the beginning and the end of the school year. What is the difference between the maximum and minimum values for x?
 
−
(A)0 (B20(C)40 (D)60 (E)80
 
  
 
13. What is the sum of all the solutions of x=|2x-|60-2x||?
 
13. What is the sum of all the solutions of x=|2x-|60-2x||?
Line 180: Line 154:
 
== Problem 8 ==
 
== Problem 8 ==
  
 +
A ticket to a school play cost <math>x</math> dollars, where <math>x</math> is a whole number. A group of 9<sup>th</sup> graders buys tickets costing a total of &#36;<math>48</math>, and a group of 10<sup>th</sup> graders buys tickets costing a total of &#36;<math>64</math>. How many values for <math>x</math> are possible?
  
−
<math>
+
<math>\textbf{(A)}\ 1 \qquad \textbf{(B)}\ 2 \qquad \textbf{(C)}\ 3 \qquad \textbf{(D)}\ 4 \qquad \textbf{(E)}\ 5</math>
−
\mathrm{(A)}\
 
−
\qquad
 
−
\mathrm{(B)}\  
 
−
\qquad
 
−
\mathrm{(C)}\  
 
−
\qquad
 
−
\mathrm{(D)}\  
 
−
\qquad
 
−
\mathrm{(E)}\  
 
−
</math>
 
  
 
[[2010 AMC 10B Problems/Problem 8|Solution]]
 
[[2010 AMC 10B Problems/Problem 8|Solution]]
Line 197: Line 162:
 
== Problem 9 ==
 
== Problem 9 ==
  
 +
Lucky Larry's teacher asked him to substitute numbers for <math>a</math>, <math>b</math>, <math>c</math>, <math>d</math>, and <math>e</math> in the expression <math>a-(b-(c-(d+e)))</math> and evaluate the result. Larry ignored the parenthese but added and subtracted correctly and obtained the correct result by coincidence. The number Larry sustitued for <math>a</math>, <math>b</math>, <math>c</math>, and <math>d</math> were <math>1</math>, <math>2</math>, <math>3</math>, and <math>4</math>, respectively. What number did Larry substitude for <math>e</math>?
  
−
<math>
+
<math>\textbf{(A)}\ -5 \qquad \textbf{(B)}\ -3 \qquad \textbf{(C)}\ 0 \qquad \textbf{(D)}\ 3 \qquad \textbf{(E)}\ 5</math>
−
\mathrm{(A)}\  
 
−
\qquad
 
−
\mathrm{(B)}\  
 
−
\qquad
 
−
\mathrm{(C)}\  
 
−
\qquad
 
−
\mathrm{(D)}\  
 
−
\qquad
 
−
\mathrm{(E)}\  
 
−
</math>
 
  
 
[[2010 AMC 10B Problems/Problem 9|Solution]]
 
[[2010 AMC 10B Problems/Problem 9|Solution]]
Line 214: Line 170:
 
== Problem 10 ==
 
== Problem 10 ==
  
 +
Shelby drives her scooter at a speed of <math>30</math> miles per hour if it is not raining, and <math>20</math> miles per hour if it is raining. Today she drove in the sun in the morning and in the rain in the evening, for a total of <math>16</math> miles in <math>40</math> minutes. How many minutes did she drive in the rain?
  
−
<math>
+
<math>\textbf{(A)}\ 18 \qquad \textbf{(B)}\ 21 \qquad \textbf{(C)}\ 24 \qquad \textbf{(D)}\ 27 \qquad \textbf{(E)}\ 30</math>
−
\mathrm{(A)}\  
 
−
\qquad
 
−
\mathrm{(B)}\  
 
−
\qquad
 
−
\mathrm{(C)}\  
 
−
\qquad
 
−
\mathrm{(D)}\  
 
−
\qquad
 
−
\mathrm{(E)}\  
 
−
</math>
 
  
 
[[2010 AMC 10B Problems/Problem 10|Solution]]
 
[[2010 AMC 10B Problems/Problem 10|Solution]]
  
 
== Problem 11 ==
 
== Problem 11 ==
−
 
+
A shopper plans to purchase an item that has a listed price greater than &#36;<math>100</math> and can use any one of the three coupns. Coupon A gives <math>15\%</math> off the listed price, Coupon B gives &#36;<math>30</math> off the listed price, and Coupon C gives <math>25\%</math> off the amount by which the listed price exceeds
 +
&#36;<math>100</math>. <br/>
 +
Let <math>x</math> and <math>y</math> be the smallest and largest prices, respectively, for which Coupon A saves at least as many dollars as Coupon B or C. What is <math>y</math> − <math>x</math>?
  
 
<math>
 
<math>
−
\mathrm{(A)}\  
+
\mathrm{(A)}\ 50
 
\qquad
 
\qquad
−
\mathrm{(B)}\  
+
\mathrm{(B)}\ 60
 
\qquad
 
\qquad
−
\mathrm{(C)}\  
+
\mathrm{(C)}\ 75
 
\qquad
 
\qquad
−
\mathrm{(D)}\  
+
\mathrm{(D)}\ 80
 
\qquad
 
\qquad
−
\mathrm{(E)}\  
+
\mathrm{(E)}\ 100
 
</math>
 
</math>
  
Line 248: Line 197:
 
== Problem 12 ==
 
== Problem 12 ==
  
 +
At the beginning of the school year, <math>50\%</math> of all students in Mr. Wells' math class answered "Yes" to the question "Do you love math", and <math>50\%</math> answered "No." At the end of the school year, <math>70\%</math> answered "Yes" and <math>30\%</math> answerws "No." Altogether, <math>x\%</math> of the students gave a different answer at the beginning and end of the school year. What is the difference between the maximum and the minimum possible values of <math>x</math>?
  
−
<math>
+
<math>\textbf{(A)}\ 0 \qquad \textbf{(B)}\ 20 \qquad \textbf{(C)}\ 40 \qquad \textbf{(D)}\ 60 \qquad \textbf{(E)}\ 80</math>
−
\mathrm{(A)}\  
 
−
\qquad
 
−
\mathrm{(B)}\  
 
−
\qquad
 
−
\mathrm{(C)}\  
 
−
\qquad
 
−
\mathrm{(D)}\  
 
−
\qquad
 
−
\mathrm{(E)}\  
 
−
</math>
 
  
 
[[2010 AMC 10B Problems/Problem 12|Solution]]
 
[[2010 AMC 10B Problems/Problem 12|Solution]]
  
 
== Problem 13 ==
 
== Problem 13 ==
−
 
+
What is the sum of all the solutions of <math>x = \left|2x − |60 − 2x|\right|</math>?
  
 
<math>
 
<math>
−
\mathrm{(A)}\  
+
\mathrm{(A)}\ 32
 
\qquad
 
\qquad
−
\mathrm{(B)}\  
+
\mathrm{(B)}\ 60
 
\qquad
 
\qquad
−
\mathrm{(C)}\  
+
\mathrm{(C)}\ 92
 
\qquad
 
\qquad
−
\mathrm{(D)}\  
+
\mathrm{(D)}\ 120
 
\qquad
 
\qquad
−
\mathrm{(E)}\  
+
\mathrm{(E)}\ 124
 
</math>
 
</math>
  

Revision as of 12:00, 2 April 2010


13. What is the sum of all the solutions of x=|2x-|60-2x||? (A)32 (B)60 (C)92 (D)120 (E)124

14.The average of the numbers 1, 2, 3, ...98, 99, and x is 100x.What is x? (A)49/101 (B)50/101 (C)1/2 (D)51/101 (E)50/99

15.On a 50-question multiple choice contest, students recieve 4 points for a correct answer, 0 points for left blank, and -1 point for an incorrect answer. Jesse's total score on the contest was 99. What is the maximum number of questions she could have answered correctly? (A)25 (B)27 (C)29 (D)31 (E)33

16. A square of side length 1 and a circle of radius sqrt(3)/3 share the same center. What is the area inside the circle, but outside the square? (A)(pi/3)-1 (B)(2pi/9)-sqrt(3)/3 (C)pi/18 (D)1/4 (E)2pi/9

17.Every high school in a city sent a team of 3 students to a math contest. Each participant in the contest recieved a different score. Andrea's score was the median, and hers was the highest score on her team. Andrea's teammates Beth and Carla placed 37th and 64th, respectively. How many schools are in the city? (A)22 (B)23 (C)24 (D)25 (E)26

18.Positive integers a, b, and c are randomly and independently chosen with replacement from the set {1, 2, 3, ..., 2010}. What is the probability that abc+ab+a is divisible by 3? (A)1/3 (B)6 (C)4sqrt(3) (D)12 (E)18

19. A circle with center O has area 156pi. Triangle ABC is equilateral, BC is a chord on the circle, OA=4sqrt(3), and point O is outside triangle ABC. What is the side length of triangle ABC? (A)2sqrt(3) (B)6 (C)4sqrt(3) (D)12 (E)18

20. 2 circles lie outside of regular hexagon ABCDEF. The first is tangent to Ab, and the second is tangent to DE. Both are tangent to lines BC and FA. What is the ratio of the area of the second circle to the area of the first circle? (A)18 (B)27 (C)36 (D)81 (E)108

21.A palindrom between 1000 and 10000 is chosen at random. WHat is the probability that it is divisible by 7? (A)1/10 (B)1/9 (C)1/7 (D)1/6 (E)1/5

22.Seven distinct pieces of candy are to be stored among 3 bags. The red bad and the blue bag must recieve at least one piece of candy; the white bag may remain empty. How many arrangements are possible? (A)1930 (B)1931 (C)1932 (D)1933 (E)1934

23.The entries in a 3x3 array include all digits from 1 to 9, arranged so that the entries in every row and column are in increasing order. How many such arrays are there? (A)18 (B)24 (C)36 (D)42 (E)60

24.A high school b-ball game between the R's and the W's was tied at the end of the first quarter. The number of point the R's scored in each of the four quarters formed an increasing geometric sequence, and the number of points the W's scored in each of the 4 quarters formed an increasing arithmetic sequence. At the end of the 4th quarter, the the R's had won by one point. Neither team scored more than 100 points. What was the total number of points scored by the two teams in the first half? (A)30 (B)31 (C)32 (D)33 (E)34

25. Let a>0, and let P(x) be a polynomial with integer coefficients such that: P(1)=P(3)=P(5)=P(7)=a, and P(2)=P(4)=P(6)=P(8)=-a. What is the smallest possible value of a? (A)105 (B)315 (C)845 (D)7! (E)8!


Problem 1

1. What is $100(100-3)-(100\times100-3)$?

$\mathrm{(A)}\ -20,000 \qquad \mathrm{(B)}\ -10,000 \qquad \mathrm{(C)}\ -297 \qquad \mathrm{(D)}\ -6 \qquad \mathrm{(E)}\ 0$


Solution

Problem 2

Makarla attended two meetings during her $9$-hour work day. The first meeting took $45$ minutes and the second meeting took twice as long. What percent of her work day was spent attending meetings?

$\textbf{(A)}\ 15 \qquad \textbf{(B)}\ 20 \qquad \textbf{(C)}\ 25 \qquad \textbf{(D)}\ 30 \qquad \textbf{(E)}\ 35$


Solution

Problem 3

A drawer contains red, green, blue, and white socks with at least 2 of each color. What is the minimum number of socks that must be pulled from the drawer to guarantee a matching pair?

$\mathrm{(A)}\ 3 \qquad \mathrm{(B)}\ 4 \qquad \mathrm{(C)}\ 5 \qquad \mathrm{(D)}\ 8 \qquad \mathrm{(E)}\ 9$

Solution

Problem 4

For a real number $x$, define $\heartsuit(x)$ to be the average of $x$ and $x^2$. What is $\heartsuit(1)+\heartsuit(2)+\heartsuit(3)$?

$\mathrm{(A)}\ 3 \qquad \mathrm{(B)}\ 6 \qquad \mathrm{(C)}\ 10 \qquad \mathrm{(D)}\ 12 \qquad \mathrm{(E)}\ 20$

Solution

Problem 5

A month with $31$ days has the same number of Mondays and Wednesdays.How many of the seven days of the week could be the first day of this month?

$\textbf{(A)}\ 2 \qquad \textbf{(B)}\ 3 \qquad \textbf{(C)}\ 4 \qquad \textbf{(D)}\ 5 \qquad \textbf{(E)}\ 6$

Solution

Problem 6

A circle is centered at $O$, $\overbar{AB}$ (Error compiling LaTeX. Unknown error_msg) is a diameter and $C$ is a point on the circle with $\angle COB = 50^\circ$. What is the degree measure of $\angle CAB$?

$\mathrm{(A)}\ 20 \qquad \mathrm{(B)}\ 25 \qquad \mathrm{(C)}\ 45 \qquad \mathrm{(D)}\ 50 \qquad \mathrm{(E)}\ 65$

Solution

Problem 7

A triangle has side lengths $10$, $10$, and $12$. A rectangle has width $4$ and area equal to the area of the rectangle. What is the perimeter of this rectangle?

$\mathrm{(A)}\ 16 \qquad \mathrm{(B)}\ 24 \qquad \mathrm{(C)}\ 28 \qquad \mathrm{(D)}\ 32 \qquad \mathrm{(E)}\ 36$

Solution

Problem 8

A ticket to a school play cost $x$ dollars, where $x$ is a whole number. A group of 9th graders buys tickets costing a total of $$48$, and a group of 10th graders buys tickets costing a total of $$64$. How many values for $x$ are possible?

$\textbf{(A)}\ 1 \qquad \textbf{(B)}\ 2 \qquad \textbf{(C)}\ 3 \qquad \textbf{(D)}\ 4 \qquad \textbf{(E)}\ 5$

Solution

Problem 9

Lucky Larry's teacher asked him to substitute numbers for $a$, $b$, $c$, $d$, and $e$ in the expression $a-(b-(c-(d+e)))$ and evaluate the result. Larry ignored the parenthese but added and subtracted correctly and obtained the correct result by coincidence. The number Larry sustitued for $a$, $b$, $c$, and $d$ were $1$, $2$, $3$, and $4$, respectively. What number did Larry substitude for $e$?

$\textbf{(A)}\ -5 \qquad \textbf{(B)}\ -3 \qquad \textbf{(C)}\ 0 \qquad \textbf{(D)}\ 3 \qquad \textbf{(E)}\ 5$

Solution

Problem 10

Shelby drives her scooter at a speed of $30$ miles per hour if it is not raining, and $20$ miles per hour if it is raining. Today she drove in the sun in the morning and in the rain in the evening, for a total of $16$ miles in $40$ minutes. How many minutes did she drive in the rain?

$\textbf{(A)}\ 18 \qquad \textbf{(B)}\ 21 \qquad \textbf{(C)}\ 24 \qquad \textbf{(D)}\ 27 \qquad \textbf{(E)}\ 30$

Solution

Problem 11

A shopper plans to purchase an item that has a listed price greater than $$100$ and can use any one of the three coupns. Coupon A gives $15\%$ off the listed price, Coupon B gives $$30$ off the listed price, and Coupon C gives $25\%$ off the amount by which the listed price exceeds $$100$.
Let $x$ and $y$ be the smallest and largest prices, respectively, for which Coupon A saves at least as many dollars as Coupon B or C. What is $y$ − $x$?

$\mathrm{(A)}\ 50 \qquad \mathrm{(B)}\ 60 \qquad \mathrm{(C)}\ 75 \qquad \mathrm{(D)}\ 80 \qquad \mathrm{(E)}\ 100$

Solution

Problem 12

At the beginning of the school year, $50\%$ of all students in Mr. Wells' math class answered "Yes" to the question "Do you love math", and $50\%$ answered "No." At the end of the school year, $70\%$ answered "Yes" and $30\%$ answerws "No." Altogether, $x\%$ of the students gave a different answer at the beginning and end of the school year. What is the difference between the maximum and the minimum possible values of $x$?

$\textbf{(A)}\ 0 \qquad \textbf{(B)}\ 20 \qquad \textbf{(C)}\ 40 \qquad \textbf{(D)}\ 60 \qquad \textbf{(E)}\ 80$

Solution

Problem 13

What is the sum of all the solutions of $x = \left|2x − |60 − 2x|\right|$ (Error compiling LaTeX. Unknown error_msg)?

$\mathrm{(A)}\ 32 \qquad \mathrm{(B)}\ 60 \qquad \mathrm{(C)}\ 92 \qquad \mathrm{(D)}\ 120 \qquad \mathrm{(E)}\ 124$

Solution

Problem 14

$\mathrm{(A)}\ \qquad \mathrm{(B)}\ \qquad \mathrm{(C)}\ \qquad \mathrm{(D)}\ \qquad \mathrm{(E)}$

Solution

Problem 15

$\mathrm{(A)}\ \qquad \mathrm{(B)}\ \qquad \mathrm{(C)}\ \qquad \mathrm{(D)}\ \qquad \mathrm{(E)}$

Solution

Problem 16

$\mathrm{(A)}\ \qquad \mathrm{(B)}\ \qquad \mathrm{(C)}\ \qquad \mathrm{(D)}\ \qquad \mathrm{(E)}$

Solution

Problem 17

$\mathrm{(A)}\ \qquad \mathrm{(B)}\ \qquad \mathrm{(C)}\ \qquad \mathrm{(D)}\ \qquad \mathrm{(E)}$

Solution

Problem 18

$\mathrm{(A)}\ \qquad \mathrm{(B)}\ \qquad \mathrm{(C)}\ \qquad \mathrm{(D)}\ \qquad \mathrm{(E)}$

Solution

Problem 19

$\mathrm{(A)}\ \qquad \mathrm{(B)}\ \qquad \mathrm{(C)}\ \qquad \mathrm{(D)}\ \qquad \mathrm{(E)}$

Solution

Problem 20

$\mathrm{(A)}\ \qquad \mathrm{(B)}\ \qquad \mathrm{(C)}\ \qquad \mathrm{(D)}\ \qquad \mathrm{(E)}$

Solution

Problem 21

$\mathrm{(A)}\ \qquad \mathrm{(B)}\ \qquad \mathrm{(C)}\ \qquad \mathrm{(D)}\ \qquad \mathrm{(E)}$

Solution

Problem 22

$\mathrm{(A)}\ \qquad \mathrm{(B)}\ \qquad \mathrm{(C)}\ \qquad \mathrm{(D)}\ \qquad \mathrm{(E)}$

Solution

Problem 23

$\mathrm{(A)}\ \qquad \mathrm{(B)}\ \qquad \mathrm{(C)}\ \qquad \mathrm{(D)}\ \qquad \mathrm{(E)}$

Solution

Problem 24

$\mathrm{(A)}\ \qquad \mathrm{(B)}\ \qquad \mathrm{(C)}\ \qquad \mathrm{(D)}\ \qquad \mathrm{(E)}$

Solution

Problem 25

$\mathrm{(A)}\ \qquad \mathrm{(B)}\ \qquad \mathrm{(C)}\ \qquad \mathrm{(D)}\ \qquad \mathrm{(E)}$

Solution

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