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 By: JessicaTan (offline)  Sunday, January 06 2013 @ 08:20 AM CST (Read 1115 times)
JessicaTan

Eldrick is 3/5 as old as his brother. In 21 years time, he will be 5/6 as old as his brother. How old will Eldrick be in 21 years time?
(ans : 30 years old)

thanks
Jessica

Regular Member

Registered: 10/17/09
Posts: 82

 By: echeewh (offline)  Sunday, January 06 2013 @ 03:33 PM CST
echeewh

Hi Jessica,

Folllowing pls find my worked solution...

(now)
E : B
3 : 5

(21yrs time)
E : B
5 : 6

Apply Unchanged Difference concept (age difference between 2 persons remains the same now and the future), we have ...

Age difference (now) = 5p - 3p = 2p
Age difference (21yrs time) = 6u - 5u = 1u

Hence, 1u = 2p

so the ratio for (21yrs time) becomes ...

(21yrs time)
E : B
10 : 12

comparing E's age now and future,

Difference = 10p - 3p = 7p
7p --> 21 years
1p --> 3

E's age (21yrs time) = 10p --> 10 × 3 = 30 yrs old

===============

Trust this helps.

Do let me know again should there be any clarification.

Cheers,
Edward

Active Member

Registered: 04/21/11
Posts: 627

 By: JessicaTan (offline)  Monday, January 07 2013 @ 04:33 AM CST
JessicaTan

Regular Member

Registered: 10/17/09
Posts: 82

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