Adding and Subtracting Big Numbers
Develop efficient strategies and use appropriate digital tools for solving problems involving addition and subtraction, and multiplication and division where there is no remainder.
Read this first
Split the number into tidy parts. Add the parts one at a time.
Jump 30 first. Then jump 8. That is 47 + 38.
Words you need
- Strategy
- A clever way to work something out.
- Split
- Break a number into smaller parts.
- Jump
- Move along a number line in steps.
Worked example
e.g. What is 47 + 38?
- Split 38 into 30 and 8.
- Start at 47. Jump 30. You land on 77.
- Now jump 8 more. You land on 85.
- So 47 + 38 = 85.
Jump the tens first. Then jump the ones.
Practice
The pictures fade as you go. By the last few you are on your own.
1What is 25 + 30?with a picture
Answer55.
2What is 62 - 20?with a picture
Answer42.
3What is 56 + 27?with a hint
Need a hint?
Split 27 into 20 and 7.
Answer83.
4What is 84 - 36?with a hint
Need a hint?
Take away 30 first. Then take away 6.
Answer48.
5What is 145 + 60?on your own
Answer205.
6What is 230 - 45?on your own
Answer185.
7What is 199 + 1 + 45?on your own
Answer245. Do 199 + 1 first to make 200.
Think about it
1
Why jump the tens first?
One good answerThe tens are the big part. It gets you close fast.
2
Is there only one right way?
One good answerNo. Any way that gets the right answer is fine.
Common mistakes
Splitting the wrong number.
Keep the first number whole. Split the second one.
Forgetting the second jump.
Write both parts down before you start.