2.NBT.8: Mental Math Strategies

Problem 1

Start with 381. Add 100, then subtract 10, then add 100 again. What is your final answer?

Explain the pattern you notice.

Problem 2

Start with 529. Add 100, then subtract 10, then add 100 again. What is your final answer?

Explain the pattern you notice.

Problem 3

Start with 477. Add 100, then subtract 10, then add 100 again. What is your final answer?

Explain the pattern you notice.

Problem 4

Find a quick way to solve 347 + 99 using mental math. Explain your strategy.

Problem 5

Find a quick way to solve 347 + 99 using mental math. Explain your strategy.

Problem 6

Find a quick way to solve 347 + 99 using mental math. Explain your strategy.

Problem 7

Create a mental math trick for adding 98 to any three-digit number. Show how it works with an example.

Problem 8

Create a mental math trick for adding 98 to any three-digit number. Show how it works with an example.

Problem 9

Create a mental math trick for adding 98 to any three-digit number. Show how it works with an example.

Problem 10

Create a mental math trick for adding 98 to any three-digit number. Show how it works with an example.