Subtract Doubles:

This space shuttle just left Earth. Bill, the astronaut, was so excited before takeoff that he forgot to put his snacks away! Can you help Bill find his snacks and put them away?

Here is a jar of cookies. This jar had 10 cookies before liftoff. Now it only has 5 cookies. How many cookies are floating in the air?

We can solve this problem using a doubles fact. We know that 5+5=10. This also means that 10-5=5. This is a doubles facts because 5 and 5 are the same number.

Here is a jar of crackers. It had 14 crackers in it before liftoff, but now there are only 7 crackers left. How many crackers floated out of the jar? We can use the subtraction sentence 14-7.

Let’s help Bill solve this subtraction sentence. First, think of the doubles fact. Yes! 7+7=14. That means 14-7=7. There are 7 cookies missing.

This jar used to have 8 granola bars in it. Now it only has 4 granola bars. What subtraction sentence could we use? Very good! 8-4.

Hmm, there is an 8 and a 4. Could we use a doubles fact to find the number of missing granola bars? Yes! 4+4=8, which also means 8-4=4. There are 4 missing granola bars.

Here is the last jar. It had 18 candies in it before liftoff. Now there are only 9 left. I wonder if we can solve this problem with a doubles fact.

Let’s think of the subtraction sentence first. 18-9. Do you know what doubles fact we could use? Correct! 9+9=18. That means 18-9=9. There are 9 pieces of candy missing.

Thank you for using the doubles strategy to help Bill subtract today. Now his snacks are put away and he can keep exploring space. Great job!