In a computer repair shop the ratio of the number of CPUs to

PROMPT ANALYSIS
Let total number of device be T
CPU = 2T/17
Motherboard = 3T/17
Keyboards = 5T/17
Mouse pad = 7T/17

SUPERSET
T will a natural number multiple of 17.

TRANSLATION
In order to find T:
1# we need exact value of T
2# another equation with T as variable.

Statement Analysis

St 1: Since T/17 will yeild an integer, 5T/17 will also be an integer.Between 6 and 14, only 10 is a mutiple of 5. Hence no. of keyboards =10. No. of motherboards = 6 and T =38. Therfore the difference is 4.ANSWER. Option b,c and e eliminated.

St 2: 7T/17 -2T/17 = 10 or 5T/17 = 10 or T=38. Hence no. of keyboards =10. No. of motherboards = 6. Therfore the difference is 4.ANSWER. Option a eliminated.

Option D

The thing with ratio's i keep stumbling on is that, for example, a ratio 2:3 is not simply a number but a relationship that has an unspecified shared variable.

This isn't apparent to me when I approach these problems, simply running into them to solve and move on. Thats why I keep tripping up on fairly simple Quant questions like this.

So in 2:3 its actually 2x:3x, where x is that shared unspecified variable. It helps me to think of that when I see a ratio problem. All the comments specified that in their explanations, but I wanted to make sure I spell it out as a reminder to myself that I trip on this aspect.

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