enigma123 wrote:

A growing chocolate company recently upgraded its production plant, such that its new production company capacity was between 8 and 9 times as great as its old production capacity. Which of the following could represent the company's original production capacity in kilograms per hour and its new production capacity in kilograms per hour, respectively?

1. 13 & 107

2. 48 and 379

3. 67 and 591

A) 1 only

B) 2 only

C) 1 & 2 only

D) 1 and 3 only

E) 1,2 and 3.

Can someone please explain step by step procedure to solve this question?

Dear

enigma123,

I'm happy to help with this.

This question is a good no-calculator work-out with basic arithmetic. Make sure you are practicing no-calculator math every day. See this article for more on number sense:

http://magoosh.com/gmat/2012/number-sense-for-the-gmat/Basically, want to calculator 8 times the smaller number and 9 times the smaller number, and verify whether the larger number is between these two.

With the first, we can do ordinary multiplication. This should be too bad:

8*13 = 104

9*13 = 117

and 107 is between these two. Choice #1 is possible.

For the next two, the smaller number of the pair is a bit larger, so we will use anther trick.

Obviously, 10*48 = 480. Start there.

Now, subtract 48. 480 - 48 = 432. That must be 9*48

Now, subtract 48 again. 432 - 48 = 384. That must be 8*48

Notice that 379 is not between these two. Therefore, choice #2 is not possible.

For the third line, obviously 67*10 = 670.

Subtract 67. 670 - 67 = 603. That must be 9*67.

Notice that we don't even need to do the next subtraction, because 591 is very close to 603, and we subtract 67 from 603, we will be way below 591. 591 is clearly less than 9*67 and more than 8*67, so choice #3 is possible.

Choices #1 & #3 are possible. Answer =

(D).

Does all this make sense?

Mike

_________________

Mike McGarry

Magoosh Test Prep

Education is not the filling of a pail, but the lighting of a fire. — William Butler Yeats (1865 – 1939)