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Question 3

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by Bullzi » Fri Sep 18, 2015 5:00 am
Hello..

I am not a regular here, so, I am not sure if I am allowed to 'try' and post answers even if am not sure about an approach. Please remove my post if it violates rules, apologies!

Anyway, factoring 770 would result in the factors being 11, 7, 5 and 2. From the question, since 1 < w < x < y < z, w and z need to be 2 and 11. So, if that's correct, then w + z should be 13..

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by GMATGuruNY » Fri Sep 18, 2015 5:26 am
oquiella wrote:3. If the product of the integers w,x,y, and z is 770, and if 1 < w < x < y < z, what is the value of w + z?

A. 10

B. 13

C. 16

D. 18

E. 21
770 = 2*5*7*11.
Since wxyz = 770 and 1<w<x<y<z, w=2, x=5, y=7 and z=11.
Thus, w+z = 2+11 = 13.

The correct answer is B.
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by oquiella » Fri Sep 18, 2015 7:45 am
GMATGuruNY wrote:
oquiella wrote:3. If the product of the integers w,x,y, and z is 770, and if 1 < w < x < y < z, what is the value of w + z?

A. 10

B. 13

C. 16

D. 18

E. 21
770 = 2*5*7*11.
Since wxyz = 770 and 1<w<x<y<z, w=2, x=5, y=7 and z=11.
Thus, w+z = 2+11 = 13.

The correct answer is B.

How Did you factor 770 so quickly?
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by Brent@GMATPrepNow » Fri Sep 18, 2015 7:48 am
oquiella wrote: How Did you factor 770 so quickly?
Here's a free video on how to find the prime factorization of a number: https://www.gmatprepnow.com/module/gmat- ... /video/825

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by [email protected] » Fri Sep 18, 2015 9:26 am
Hi oquiella,

One of the great aspects of the 'math' behind factoring is that you can do the factoring in any order and you'll still get to the same result...

With 770, a few Number Properties stand out, so your first 'factor' would likely either be 2 (since 770 is EVEN), 7 (since 7 divides into 700 and 70) or 10 (since 770 ends in a 0). Let's go for the biggest option first....10

770 = (77)(10)

From here, you can further break down each of the two 'pieces'....

77 = (7)(11)
10 = (2)(5)

770 = (2)(5)(7)(11)

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