5th grader needs reading problem help!

[tmm2450]

Roger is planning a picnic. He will invite two times as many boys as girls. If he invites 18 people, how many boys and how many girls will get invitations?

So far, I have divided 18/2 for 9......

 

[mmm4444bot]

So far, I have divided 18/2 for 9

18/2 does not work because Roger did not invite the same number of girls as boys. Dividing 18 guests by 2 simply splits the guests evenly in half: 9 boys and 9 girls. The number of boys needs to be twice the number of girls.

In other words, there are two parts boys to one part girls. That's three parts total, that make up the 18 guests.

Hence, divide 18 by three, to get the number of people in each part.

One part will be the number of girls, and the other two parts combined will be the number of boys.

This is a ratio exercise, so you could also set up a proportion, to arrive at the same reasoning above. Have you learned about proportions, yet?



Alternatively, if you don't want to think about ratios, you could get the answer using algebra, by setting up a system of equations to solve. But, I'm thinking that 5th graders (in general) don't know algebra.

 

[tmm2450]

I got it!

I figured it out before your reply, but thank you! You helped me double check my work.