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.

 

[Dick]

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.

 

[Dick]

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

 

[Dick]

(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..

 

[Dick]

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?

 

[Dick]

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

 

[Dick]

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!