Help me with my son's homework please!!!

[janabell]

In a roller blade race, Grant is 5 meters ahead of Cathy. Mike is 7 meters behind Cathy. Joey is 4 meters ahead of Mike. How many meters is Grant ahead of Joey?

I used a number line to solve this....is there a different way? I want to explain this to my son, but that's the only way I could get the right answer... Thank you!

 

[rbcc]

Hi,

I think I got it

the first thing you should do is write down a system of equations

Let C represent Cathy
Let G represent Grant
Let M represent Mike
let J represent Joey

so we have

1) C+5=G
2) M+7=C
3) M+4=J

and we want something with G and J so look at which equations have those variables
1) C+5=G
3) M+4=J

but then we don't want the C and M in there.
2) M=C-7 sub that in to 3 so
3)M+4=J
2 into 3) C-7+4=J
and you get 4)C-3=J

not lets get rid of the "C"
1) C=G-5
sub that into 4)
G-5-3=J
G-8=J

hope that helps
rbcc

 

[janabell]

Thank you for your explanation.... I used a number line and came up with the answer 8...which is the right answer.... My son is only in the 3rd grade.... can you simplify your answer any so that it will make sense to him? At first, I wrote down Grant, Cathy, Joey and Mike....and then tried to place numbers beside each one's names, but couldn't do it that way....when I drew a number line, with no numbers...just dots....and put Grant at the end, counting backwards, I got the right answer...and that seemed so simple for me. Any other input you could give would be appreciated.

 

[wjm11]

I used a number line and came up with the answer 8...which is the right answer.... My son is only in the 3rd grade....

Janabell,

rbcc gave you a correct algebraic approach. Obviously, that is not what is intended for 3rd grade however. I think your number line approach was an excellent choice. Hopefully, it made sense to your son.

 

[janabell]

Thank you everyone for your help! Glad I found this site...I think I'll be using it a lot in the years ahead!