Math story problem with fractions that I am stuck on.

kkaterr
A guy spends 1/6 of his life as a boy, 1/8 as a youth, 1/2 as a man and 15 years as a mature adult. I got about 70 by trial and error but I need to know exactly how to solve it.

Homework Helper
Let the variable L be the length of his life. Add up all of the parts you've got and equate it to L. Now solve for L.

kkaterr
I do that and get 15.79. That can't be right.

Homework Helper
I do that and get 15.79. That can't be right.

No, it isn't. Show what you did.

kkaterr
(1/6)+(1/8)+(1/2)+15

Homework Helper
(1/6)+(1/8)+(1/2)+15

One sixth of his life is L/6. What's one eighth of his life? What's the total?

kkaterr
Going by your logic one eighth would be L/8, I'm not sure what the total is..

Homework Helper
Going by your logic one eighth would be L/8, I'm not sure what the total is..

The total is his whole life. That's L. What's the sum that is equal to L? You are doing fine so far. Write the sum that is equal to L.

kkaterr
L/6+L/8+L/2=L
Like that?

Homework Helper
L/6+L/8+L/2=L
Like that?

Close. What about the 15? Where does that go?

kkaterr
L/6+l/8+l/2+15=l

Homework Helper
L/6+l/8+l/2+15=l

Yes! Now can you use algebra to solve for L? It is pretty close to 70.

kkaterr
thank you!