2016 AMC 10A Problems/Problem 6

Problem

Star lists the whole numbers $1$ through $30$ once. Emilio copies Star's numbers, replacing each occurrence of the digit $2$ by the digit $1$ . Star adds her numbers and Emilio adds his numbers. How much larger is Star's sum than Emilio's?

$\textbf{(A)}\ 13\qquad\textbf{(B)}\ 26\qquad\textbf{(C)}\ 102\qquad\textbf{(D)}\ 103\qquad\textbf{(E)}\ 110$

Solution

For every tens digit 2, we subtract 10, and for every units digit 2, we subtract 1. Because 2 appears 10 times as a tens digit and 2 appears 3 times as a units digit, the answer is $10\cdot 10+1\cdot 3=\boxed{\textbf{(D) }103.}$

Video Solution (HOW TO THINK CRITICALLY!!!)

https://youtu.be/qrgPsA9AQLA. (short and simple!)

Education, the Study of Education.

Video Solution

https://youtu.be/XXX4_oBHuGk https://youtu.be/8i_NYG3aRxE

2016 AMC 10A (Problems • Answer Key • Resources)
Preceded by Problem 5	Followed by Problem 7
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All AMC 10 Problems and Solutions

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2016 AMC 10A Problems/Problem 6

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Solution

Video Solution (HOW TO THINK CRITICALLY!!!)

Video Solution

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