Difference between revisions of "2017 AMC 8 Problems/Problem 10"

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==Solution==
 
==Solution==
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There are <math>5 \choose 3</math> possible groups of cards that can be selected. If <math>4</math> is largest card selected, then the other two cards must be either <math>1</math>, <math>2</math>, or <math>3</math>, for a total <math>3 \choose 2</math> groups of cards. Then the probability is just <math>{\frac{{3 \choose 2}}{{5 \choose 3}}} = \boxed{{\textbf{(C) }} {\frac{3}{10}}}</math>
  
 
==See Also==
 
==See Also==

Revision as of 16:22, 22 November 2017

Problem 10

A box contains five cards, numbered 1, 2, 3, 4, and 5. Three cards are selected randomly without replacement from the box. What is the probability that 4 is the largest value selected?

$\textbf{(A) }\frac{1}{10}\qquad\textbf{(B) }\frac{1}{5}\qquad\textbf{(C) }\frac{3}{10}\qquad\textbf{(D) }\frac{2}{5}\qquad\textbf{(E) }\frac{1}{2}$

Solution

There are $5 \choose 3$ possible groups of cards that can be selected. If $4$ is largest card selected, then the other two cards must be either $1$, $2$, or $3$, for a total $3 \choose 2$ groups of cards. Then the probability is just ${\frac{{3 \choose 2}}{{5 \choose 3}}} = \boxed{{\textbf{(C) }} {\frac{3}{10}}}$

See Also

2017 AMC 8 (ProblemsAnswer KeyResources)
Preceded by
Problem 9
Followed by
Problem 11
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25
All AJHSME/AMC 8 Problems and Solutions

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