Question 269335: Uhm ,i know the answer is 36 for this . i just cant find the formula .If you can show step by step. the question is : A 48 year old man is twice as old as his son. How old was the father when he was three times as old as his son.
Answer by kensson(21)   (Show Source):
You can put this solution on YOUR website! From the first bit, we know that the father is (and has always been) 24 years older than the son, and from the second, we know that we're looking for a time when the father was three times as old. We have two equations:
f = s + 24
f = 3s
There are several ways to solve this. We can eliminate f and substitute back:
s + 24 = 3s
24 = 2s
s = 12, f = 36
Another option is to treble the first equation and eliminate s:
3f = 3s + 72
f = 3s
2f = 72
f = 36
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