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Word Problems/Math Word Problem: Age


A man is 42 years old and his daughter is 8. In how many years will the father be twice as old as his daughter?

- I've tried doing this:




(But 42+25=67, and 8+25=33 ; so 67/33 is a decimal)

I'm not quite sure exactly how to solve for it and get an exact number without any decimals.

Sorry about the delay, but I haven't been able to get on the PC over the last few days.

The numbers of years that will pass is x.
The age of the father will be 42+x and age of his daughter will be 8+x.

It says at this point, the father will be twice as old, so we get 42+x = 2(8+x).
Multiplying the right side out gives 42+x = 16+2x.
Adding -x-16 to both sides gives 26 = x.

At this point, the daughter will be 34 and the dad will be 68.

If you want a different way to do this, use a spreadsheet.
In A1, put 8.
In B1, put 42.
In A2, put =A1+1.
In B2, put =B2+1.
In C2, put =B2/B1.
Highlight rows 2 through 30, columns A through C, and do an edit-fill-down.
In row 27, there should be a 2 in column C.  The two ages are found in columns A and B.

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Scott A Wilson


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