Official Guide Explanation:
Problem Solving #108




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Solution and Metadata

Question: 108
Page: 167
Difficulty: 6 (Moderately Difficult)
Category 1: Arithmetic > Decimals >

Explanation: First, recognize that if you combine an equal number of 2's and 5's, you'll have a power of 10. In this case, we can rewrite the expression as:


= (1/(26103))

= (1/(26)) * 10-3

26 is 64, so (1/(26)) = (1/64). (1/64) is somewhere between 0.01 ((1/100)) and 0.02 ((1/50)). The exact number doesn't matter for this question, so let's call it 0.015. That gives us:

0.015 * 10-3

Move the decimal point three spaces to the left:


There are four zeros between the decimal point and the first nonzero digit. (B) is correct.

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