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Old Enough ?

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Arthur:
"When I add 4 times my age 4 years from now to 5 times my age 5 years from now, I get 10 times my current age. How old will I be 4 years from now?"
Answer: 45

Solution:

"Let x be my present age. My age 4 years from now will be x + 4, and 4 times that will be 4 (x + 4). Similarly, my age 5 years from now will be x + 5, and 5 times that will be 5 (x + 5).

Adding the two gives 10 times my current age. This gives the equation:

4 (x + 4) + 5 (x + 5) = 10 x.

Solving the above equation gives

x = (4 × 4) + (5 × 5) = 41.

Thus, I will be 45 years old 4 years from now."

Food for thought:

How do you verify the answer?
It's easy! By substitution, right?


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