math question

[rockridgecattle]

So need some help here. Have a young lad staying with us for a bit. He needs help in math...polynomials. One has me stumped.

0.2(5-2r)=0.3(1-r).....Answer is r=7. But how to get there....help me help him please. Been outta school way too long

 

[KNERSIE]

0.2(5-2r) = 0.3(1-r) .....x 10
2(5-2r) = 3(1-r) ..... multiply out
10 -4r = 3-3r ..... move both r's to same side (note that moving to other side of = makes it -
-4r +3r = 3-10 ..... solve
-r = -7 .....multiply by -1 to make it positive
r = 7

 

[ga.prime]

Good trick to get rid of the decimal at the git go, K-man.

 

[rockridgecattle]

Thanks so much...it was mulitplying by 10 that made me see the light!!! Thanks guys

 

[KNERSIE]

Thanks so much...it was mulitplying by 10 that made me see the light!!! Thanks guys

you're welcome!

 

[Brute 23]

PEMDAS
What you do to one side you have to do to the other.