# More and More Fluent

Eva was 7 years and 9 months at the time this video was made.

The Problems

At this point, Eva has had enough experience with Easy Subtraction word problems that she understands these abstractions:

• How much is 51 take away 27?
• How much is 63 take away 27?

What To Look For In This Video

• Here is how Eva computes 51 - 27:
• She starts by taking 20 from 50 to get 30.
• She then takes 7 from that 30 by counting backwards - 29, 28, 27, 26, 25, 24, 23.
• She then adds back 1 to get 24.
• She next computes 63 - 27 in the same way.
• The overall logic of her shortcut is excellent. But the execution, particularly in the first problem, is not terribly smooth. She needs to count backward from 30, stumbling a little, and then she gets confused about whether to add 1 or subtract 1 at the end. She needs my support.
• On the other hand, by the time that she gets to the second problem her fluency has improved. With only a little more practice I expect that she will be able to make this argument even more fluently still.

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