Explain two different methods you can use to calculate 70 × 6 mentally.

Method 1: 70 + 70 + 70 + 70 + 70 + 70 = 420. Method 2: 7 x 6 = 42, then multiply by 10 to get 420.

Calculate 80 × 7 mentally. Write down each step you take to solve the problem.

8 x 7 = 56, then multiply by 10 to get 560.

Grade 8th Grade · Math · 45 min

I can multiply multi-digit numbers by multiples of 10 using mental math and estimation strategies.

Khan Academy · 3:05

Multiplying by multiples of 10 | Multiplication and division | Arithmetic | Khan Academy

3 key concepts

1
One way to solve 3 × 60 is to think of it as 60 + 60 + 60, which equals 180.
2
Since 60 is the same as 6 × 10, 3 × 60 can be solved as 3 × 6 × 10, which equals 18 × 10, or 180.
3
To solve 50 × 7, you can multiply 5 × 7 to get 35, then multiply by 10 (or add a zero) to get 350.

11 questions · Multiple choice & Short answer

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“Calculate 80 × 9 using mental math strategies. Show your steps.”

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