Thread: I want to learn how to solve this (probably basic) word problem.

I would prefer to be able to write an equation that could solve this but I can not. I have spent hours thinking about this word problem, It has a picture, but I'll just describe it.

It has been a while since I was in a math class and this problem really blows my mind . Not in an angry way like the emoticon.

There are 3 different colored spheres. Red, white, and blue.

1 red sphere and 1 blue sphere weigh equally as much as 6 white spheres.

1 red sphere and 2 white spheres weigh equally as much as 3 blue spheres.

Each color of sphere has a different weight. How many white spheres will balance with 1 red sphere?

It's either 4 or 2. Its obviously not the other two multiple choice answers. 8 and 6.

Thank ya.

Let r be the number of red spheres, w be the number of whites, and b the number of blues. We have
r+b=6w and r+2w=3b ... What you need to do is to get rid of the b. Here's what I did. Rewrite the equations as

r - 6w + b = 0
r + 2w - 3b = 0

Multiply the top equation by 3 and add the two equations togeter.

3r - 18w + 3b = 0
r + 2x - 3b = 0

4 r - 16 w = 0

Can you take it from there?

This is just a matter of practice. You'll get it.

Oh wait nvm, I get it r = 4w.

Thanks a ton.

but why did you multiply the top by three?

EDIT: oh you multiplied it by three so you could eliminate the b.

Thanks again.

I can't figure out how to mark the thread as solved.