Question: Nick, Mack and Chad

Comment on Nick, Mack and Chad

how about like this, since Mack is the smallest quantity, therefore
let age of Mack be = M
let age of Nick be= M+9
let age of Chad be = (M+9)-12= M-3

Quantity A => Mack age in 2 years = M+2
Quantity B => Chad age 1 year ago = M-3

subtracting M from both quantities we get
2 > -3
therefore QA> QB
hence A answer
greenlight-admin's picture

That looks great. You made one small mistake though.
Chad's age 1 year ago = (M-3)-1 = M-4

alright thanks :)

So I have another way
Macks age: M
Nicks age: M+9
Chads age: (M+9)-12-1 ( Basically took nick's age which is m+9 , minus 12 )

I then solved M+9-12=0

I then substituted M for Qty A and B , and found Qty A to be greater and hence chose A

greenlight-admin's picture


I thought on CQ's you couldn't subtract variables on numbers?
greenlight-admin's picture

Adding and subtracting variables is perfectly valid when solving Quantitative Comparison questions. More here:

N = M+9
C = N-12

M = N-9+2 = N-7
C = N-12-1 = N-13

bigger quantity subtraction will yield smaller quantity
so (A)

Awesome! The tables work really well.

Thanks, I used before the multivariable approach but this one saves a lot of time in questions like this one!.

Can we write everything equaling nick's age, as such:
Then we can see M must be older than C and deduce that M's age in two years will clearly be greater than C's age a year ago. Or am I missing a concept somewhere?
greenlight-admin's picture

That's a great approach! Pure logic and number sense!

In the given question -

N = 9+M

C = 12-N


if current age is 100 for M then -> M=100, N=109, C=97

if Mack's age after 2 years is 102, then N=111, C=99.

And Nicks 1yr ago age is 98. here 102>98 hence A.

How about this solution Brent? Is it a valid one?
greenlight-admin's picture

Your equation C = 12 - N does not match the given information.

We're told that Chad is 12 years younger than Nick.
So, for example, it could be the case that Chad is 3 and Nick is 15.
In other words, C = 3 and N = 15
When we plug these values into your equation, C = 12 - N, we get: 3 = 12 - 15, which is not true (12 - 15 = -3, not 3).

Likewise, it could be the case that Chad is 20 and Nick is 32.
However when we plug these values into your equation, we get: 20 = 12 - 32, which is not true.

The same applies to the values you are using: M = 100, N = 109, C = 97.
If we plug N = 109, C = 97 into your equation, we get: 97 = 12 - 109, which is not true.

If Chad is 12 years younger than Nick, then the correct equation is: C = N - 12

Does that help?

Thanks Understood!!

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