Student Self Check

Carlos’s Work

Work Time

Carlos's Work

The problem:

A waiter at a restaurant shares his tips with the busboy in a ratio of 5:2. If the waiter had $45 after sharing his tips, how much did he give the busboy?

Carlos says:

“I used a double number line. First I made a number line for the waiter that went from 0 to 65, counting by 5s. Then I made a number line for the busboy. I lined up $5 for the waiter with $1 for the busboy. Then I could see what lined up with $45 for the waiter. Since $9 lines up with $45 for the waiter, the waiter gave the busboy $9.”

  • What mistake did Carlos make?
  • Is there a way he could have used a double number line to solve the problem correctly? Explain.