Adding & Subtracting Large Numbers

Adding & subtracting by focusing on the place value of the digits

3.4

Guiding Questions

• How can understanding place value help you solve addition and subtraction problems with larger numbers?

Warm Up: Closest Estimate

• 42 x 18 What’s the closest estimate?

420 800 840

Would the estimate we chose be greater than or less than the actual answer? How do you know that? Turn & talk, figure it out without finding the actual answer

Adding & Subtracting Large Numbers

• Today we will work with numbers larger than 10,000. We will start by solving related problems. As I show each one, think about how the answer to the previous problem can help you solve the new problem. You should be able to do these mentally.

12,385 – 200 =

12,385 – 210 =

12,385 – 212 =

Story Context

• There are 12,385 people at a basketball game. If 200 of them leave the game, we know that 12,185 people are left.

• Use this story to tell me what 12,385 – 210 means. Will the answer to this problem be more or less than 12,195? How do you know?

• What about 12,385 – 212? How does that work with this story? Would the answer be more, or less, than 12,385 – 210?

More sets of problems

• 7,653 + 400 =• Compare 7,653 and the sum. Which digits are

the same? Different? Why?

• 7,653 + 420 =Compare the sum of the first problem with the sum

of this one.• 7,663 + 420 =How can the previous sum help you solve this

problem?

VERY large numbers

• 1,000 one thousand

• 10,000 ten thousand

• 100,000 one hundred thousand

• 1,000,000 one million

• 10,000,000 ten million

• 100,000,000 one hundred million

• 1,000,000,000 one billion

Place Value Chart

Billions Millions Thousands Units Decimals

Fun With Numbers

• Write down a really, really big number, something with more than 5 digits.

• Add 10 to it and show how the new number is different.

• Add or subtract a few different numbers that are multiples of 10, 100, 1,000 to your really big number and work with a partner to see how your number changes!

Guiding Questions

• How can understanding place value help you solve addition and subtraction problems with larger numbers?