On this number line, Jennifer
started at 13 and counted forward until she reached 18. Which number sentence describes
what Jennifer did, 13 plus five equals 18, 18 take away four equals 14, thirteen
plus one equals 18, 18 take away five equals 13, 13 add three equals 18?
We know that Jennifer started at
13. So the number sentences which start
at 18 don’t describe what Jennifer did. Let’s count the number of times
Jennifer counted forward: one, two, three, four, five.
So this is the number sentence
which describes what Jennifer did: the answer is 13 plus five equals 18.