To find 4 times any number, Susan uses the Double-Double strategy (multiply by 2, then by 2 again).

To find 4 times any number, Susan uses the Double-Double strategy (multiply by 2, then by 2 again). Susan wrote (2 × 9) × 2 to record how she would solve 4 × 9.

a What is 4 × 9?
b What is another way to solve 4 × 9?

Answer: a What is 4 × 9? => 36

b What is another way to solve 4 × 9? Work will vary. Example:
(4 × 4) + (4 × 5) = 16 + 20 = 36

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