Mental Math: Multiplication Strategies

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Show your work for each problem.

1.
Which strategy would be BEST for calculating ?
1. a)Double and halve
2. b)Multiply by 10, then divide by 2
3. c)Multiply by 9, then add 16
4. d)Break apart 16 into 10 + 6
2.
Use the break apart strategy: What is ?
3.
Use the multiply-by-9 trick: What is ?
4.
Calculate using the multiply-by-5 trick.
5.
What is using the multiply-by-9 trick?
1. a)60
2. b)54
3. c)56
4. d)48
6.
Use the break apart strategy to calculate .
7.
Use doubling and halving: What is ?
8.
A student calculated as follows: . What did they forget?
1. a)To subtract 15
2. b)Nothing, the answer is correct
3. c)To also calculate and add it
4. d)To divide by 2
9.
Calculate using the multiply-by-5 trick.
10.
Use doubling and halving to calculate .
11.
Using the break apart strategy, what is ?
1. a)86
2. b)88
3. c)92
4. d)96
12.
Use the near squares strategy to calculate .
13.
A book costs 19 dollars. How much do 8 books cost? Use mental math.
14.
Calculate using the double and halve strategy.
15.
A recipe needs 45 grams of sugar. You're making 6 batches. How many grams total?
16.
Which calculation shows the correct use of doubling and halving for ?
1. a)
2. b)
3. c)
4. d)
17.
What is using the multiply-by-5 trick?
18.
Calculate using the multiply-by-9 trick.