Source: Official Guide for the GMAT 13th Ed. Problem Solving; #170 Official Guide for the GMAT 2015 14th Ed. Problem Solving; #170

4

If d=1/2x5 is expressed as a terminating

If d=1/2x5 is expressed as a terminating decimal, how many nonzero digits will d have?

3 Explanations

1

Jihan Cooke

When multiplying denominator by 2'4 - did the 2'4 only distribute to the 2 '3 because the bases are the same and not to 5'7 because the bases and exponents are different?

Apr 2, 2015 • Comment

Jonathan , Magoosh Tutor

Jihan,
I think you're asking why
(2^3 * 5^7) * 2^4 = 2^7 * 5*7 ?

This is multiplication, so we're not "distributing."

(2^3 * 5^7) * 2^4 =

2^3 * 2^4 * 5^7

Apr 14, 2015 • Reply

1

Mazgab Kinde

How come 2^7 * 5^7 does not equal 10^14?

Jan 30, 2015 • Comment

, Magoosh Tutor

Hi Mazgab! Great question! You are close here but the two are different.

2^7 * 5^7 is equal to

(2 * 5) ^7

10^7

When you have the same exponent and different bases that are multiplied, you multiply the bases and leave the exponent alone.

The mistake is to think that you add the exponents together. :D

Feb 6, 2015 • Reply

1

Gravatar Mike McGarry, Magoosh Tutor

Dec 28, 2013 • Comment

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Section 5.3 Problem Solving

Section 5.3 Problem Solving

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