SOLUTION: When bob was 12 his grandmother was 5 times of his age and minus 1/2 of his sister’s age (which was half of bob’s age). Now bob’s granny is 60. How old is bob now?

Question 1156608: When bob was 12 his grandmother was 5 times of his age and minus 1/2 of his sister’s age (which was half of bob’s age). Now bob’s granny is 60. How old is bob now?
Found 3 solutions by ankor@dixie-net.com, Edwin McCravy, greenestamps:
Answer by ankor@dixie-net.com(22740)   (Show Source): You can put this solution on YOUR website!
When bob was 12 his grandmother was 5 times of his age and minus 1/2 of his sister’s age (which was half of bob’s age).
Now bob’s granny is 60. How old is bob now?
:
let y = no. of years ago that this was true.
Bob was 12, so sister was 6
5(12) - 6 = 60 - y
60 - 6 = 60 - y
y = 60 - 54
y = 6 years
:
12 + 6 = 18 yrs is Bob's present age

Answer by Edwin McCravy(20056)   (Show Source): You can put this solution on YOUR website!

When Bob was 12 Suppose y years ago Bob was 12. Then B-y = 12 his grandmother was... y years ago his grandmother was G-y 5 times of his age and minus 1/2 of his sister’s age G-y = 5(12)-1/2∙S (which was half of bob’s age). S = 1/2∙B Now bob’s granny is 60. G = 60 Solve the system: From the 5th equation substitute 60 for G in the 2nd equation. Then from the 3rd equation, substitute (1/2)B for S in the 2nd equation. B=18, S=9, x=6 Edwin

Answer by greenestamps(13200)   (Show Source): You can put this solution on YOUR website!

When Bob was 12, his sister was half his age, which is 6.

When Bob was 12, his grandmother was 5 times his age, minus half his sister's age: 5(12)-(1/2)6 = 60-3 = 57.

His grandmother is now 60, so Bill was 12 3 years ago.

ANSWER: Bob is now 15.

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