Originally Posted by CAMom
Does he know how to cross-multiply?

I'd teach him 7/10=175,104,000/X

Then you multiply the 10 times the 175,104,000=7 times x

1,751,040,000=7x

Divide both sides by 7

Is cross-multiplication learned in 5th grade?? That was my very first thought, but I didn't think I could explain it even though I could do it. (I really have a hard time getting stuff out of my head and on to paper or in words.) I always remember "x over 100 is equal to is over of" from school, but that was many moons ago...

Thanks!