Jack

10-10-2013, 12:19 PM

Five years ago, Jim was half as old as John is now. If John is six years older than Jim, how old is John now ?

(A) 22

(B) 20

(C) 24

(D) 18

Thanks!

(A) 22

(B) 20

(C) 24

(D) 18

Thanks!

View Full Version : sat math word problem

Jack

10-10-2013, 12:19 PM

Five years ago, Jim was half as old as John is now. If John is six years older than Jim, how old is John now ?

(A) 22

(B) 20

(C) 24

(D) 18

Thanks!

(A) 22

(B) 20

(C) 24

(D) 18

Thanks!

miranda

10-10-2013, 12:20 PM

Let x,y be the Jim’s and John’s age now respectively.

So, the proposition “Five years ago, Jim was half as old as John is now” can be written as

x-5=\frac{y}{2} (1)

and the proposition “John is six years older than Jim” can be written as

x=y-6 (2)

Solving the simultaneous equations (1) and (2)

2x-10=y \Rightarrow 2(y-6)-10=y \Rightarrow 2y-12-10=y \Rightarrow y=22

Therefore the correct answer is (A).

So, the proposition “Five years ago, Jim was half as old as John is now” can be written as

x-5=\frac{y}{2} (1)

and the proposition “John is six years older than Jim” can be written as

x=y-6 (2)

Solving the simultaneous equations (1) and (2)

2x-10=y \Rightarrow 2(y-6)-10=y \Rightarrow 2y-12-10=y \Rightarrow y=22

Therefore the correct answer is (A).

Jack

10-10-2013, 12:20 PM

Thank you !!

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