Swim Meet Mental Math: Make a Ten and Doubles
0 / 13Swim Meet Mental Math: Make a Ten and Doubles
Use make-a-ten, doubles, and think-addition to add and subtract within 20 in your head.
Make a ten
Get to 10 first. Then add or take away the rest.
1.
Lane 1 has 8 swimmers warming up. 5 more swimmers jump in. Break apart the 5 to make a ten.
8 + 5 = 10 + = swimmers
2.
Coach Rosa has 9 kickboards. She gets 6 more. Break apart the 6 to make a ten.
9 + 6 = 10 + = kickboards
3.
The ten frame shows 7 swim caps in a basket. Use it to find 7 + 6.
7 + = 10
7 + 6 =
4.
There are 14 towels on the bench. 6 swimmers each take one. Take away 4 to get to 10 first. Then take away the rest.
14 − 6 = 14 − 4 − = towels
Doubles and near doubles
Use doubles facts you know to solve facts you are not sure of.
5.
Match each doubles fact to its sum.
6.
Ava swam 7 laps on Monday and 8 laps on Tuesday. Which way of thinking gives the right answer for 7 + 8?
7.
Maya dove for 6 rings. Then she dove for 7 more rings. Use the double 6 + 6 to help.
6 + 7 = 6 + 6 + = rings
8.
Use each doubles fact to subtract.
8 + 8 = 16, so 16 − 8 =
9 + 9 = 18, so 18 − 9 =
Fast facts at the pool
Solve each fact in your head. Pick any strategy that helps.
9.
Think addition to subtract. What do you add to 5 to get 13?
5 + = 13, so 13 − 5 =
10.
Each swimmer's lane card shows a fact. Circle every fact that equals 9.
11.
Solve each fact. Sort it by its answer.
12.
There are 16 swimmers in the pool. 9 swimmers climb out. How many swimmers are still in the pool?
13.
Jamal says 9 + 7 has the same sum as 10 + 6. Is he right? Explain how you know.