SOLUTION: John is twice as old as his brother. Four years ago, he was four times as old as his brother. Find their present ages.

Question 230629: John is twice as old as his brother. Four years ago, he was four times as old as his brother. Find their present ages.
Answer by ankor@dixie-net.com(22740) (Show Source): You can put this solution on YOUR website!
Let j = John's present age
Let b = brother's age now
:
John is twice as old as his brother.
j = 2b
;
Four years ago, he was four times as old as his brother.
j - 4 = 4(b - 4)
j - 4 = 4b - 16
j = 4b - 16 + 4
j = 4b - 12
:
Find their present ages.
Replace j with 2b in the above equation
2b = 4b - 12
12 = 4b - 2b
12 = 2b
b = 6 yrs is bro
:
obviously, John is 12,
;
;
Prove this in the statement:
"Four years ago, he was four times as old as his brother. "
12 - 4 = 4(6 - 4)
8 = 4(2)
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