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?