Subtracting Numbers with Differences up to 10 000
In this section, I will learn how to subtract numbers by:
- estimating differences. This is an informed guess.
- using personal strategies to solve problems.
- solving real-life problems involving this topic.
What are some ways that we can subtract?
Building Base Ten Blocks
This is a little different than when we are adding. Using a place value chart will always help with this. Take a look at the example below:
1 285 - 343
This is a little different than when we are adding. Using a place value chart will always help with this. Take a look at the example below:
1 285 - 343
In this example, the place value chart helps us because it tells us what to build and what to take away.
In the example to the left, we know how to build 1 285 by looking at each digit and looking above it at the place value and the blocks needed. To build 1 285, we need: 1 thousand cube 2 hundreds flat 8 tens rods 1 unit cube |
As a result, here is what we build for 1 285 (remember, we are only building the first and larger number in the subtraction. If we look at the place value above, we know that we have to take away 3 unit cubes, 4 ten rods and 3 hundreds flats. In the picture on the right, we start taking away the blocks that we know we can take away without regrouping. What do we have left?
0 thousands cubes 9 hundreds flats 4 tens rods 2 unit cubes If we put that together we have the number: 942 |
Can we subtract 3 hundreds flats? No, there are not enough hundreds flats so we have to look next door at our thousands. We need to break apart our thousands. When we do this, we make ten new flats. Take a look at the picture on the left. The only thing left to do is take away my 3 hundreds flats and count what we left. |
Counting Up
With this strategy, we take the smaller number and count up to get to the higher number. Using a place value chart can be very helpful again, as it will help you with your adding when you are counting up. The numbers in blue are the numbers I added to get to my larger number. Take a look at the example below: 1 543 - 1 250 Think: 1 250 + 200 = 1 450 1 450 + 50 = 1 500 1 500 + 43 = 1 543 Adding together what we added we get: 200 + 50 + 43 = 293 |
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