P = Pramod age
S = Sister age
Difference of their age now = 15 yr
So :
P = S - 15
After 5 years Pramod will be 5 years older, and sister will be 5 years older.
Ratio of their age will be :
( P + 5 ) / ( S + 5 ) = 1 / 2
P = S - 15 so :
( S - 15 + 5) / ( S + 5 ) = 1 / 2
( S - 10 ) / ( S + 5 ) = 1 / 2
Now you must solve equation :
( S - 10 ) / ( S + 5 ) = 1 / 2 Multiply both sides by 2
2 ( S - 10 ) / ( S + 5 ) = 1
( 2 S - 20 ) / ( S + 5 ) = 1 Multiply both sides by S + 5
2 S - 20 = S + 5 Subtract S to both sides
2 S - 20 - S = S + 5 - S
S - 20 = 5 Add 20 to both sides
S - 20 + 20 = 5 + 20
S = 25
P = S - 15 = 10
The present age :
Pramod 10 yr
Sister 25 yr
Proof :
After 5 years Pramod will be 10 + 5 = 15 yr old.
Sister will be 25 + 5 = 30 yr old.
15 / 30 = 1 / 2
Pramod is 15 years younger than his sister after 5 years he will be half his sister age find the present age
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