SOLUTION: Bob is 5 years younger than Kyle. Four years later, Kyle will be twice as old as Bob. How old is Kyle now?

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Question 1139896: Bob is 5 years younger than Kyle. Four years later, Kyle will be twice as old as Bob. How old is Kyle now?
Found 2 solutions by josgarithmetic, greenestamps:
Answer by josgarithmetic(39620) About Me  (Show Source):
You can put this solution on YOUR website!
k, Kyle now
k-5, Bob's age now

k%2B4=2%28%28k-5%29%2B4%29
-
k%2B4=2%28k-1%29
k=2k-2-4
highlight%28k=6%29

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


The solution by the other tutor is a fine formal algebraic solution.

You can also get some good practice in logical reasoning by solving the problem informally.

The difference in their ages is 5 years now; it will always be 5 years.
Since the difference in their ages will always be 5 years, Kyle will be twice as old as Bob when Kyle is 10 and Bob is 5.
Since it is 4 years from now that Kyle will be twice as old as Bob, Kyle's age now is 10-4 = 6.