Sometimes, when given an addition problem, it is easier to solve it by regrouping the numbers by place values, and then adding and subtracting.
For example, the number 999 can also be thought of as (1000 – 1). 4997 can be thought of as (5000 – 3). 2994 can be thought of as (3000 – 6).
If we are given the problem 999 + 4997 + 2994, it is easier to regroup each number than to add each digit, one by one.
Think of 999 + 4997 + 2994 as (1000 – 1) + (5000 – 3) + (3000 – 6). Or (1000 + 5000 + 3000) – 1 – 3 – 6. This is the same as (1000 + 5000 + 3000) – (1 + 3 + 6).
We regroup this as 9000 – 10, and the answer is 8990.
Let us try another example. What is 96 + 898 + 697? We regroup this as (100 – 4) + (900 – 2) + (700 – 3).
This is the same as 1700 – 9, so the answer is 1691.
For example, the number 999 can also be thought of as (1000 – 1). 4997 can be thought of as (5000 – 3). 2994 can be thought of as (3000 – 6).
If we are given the problem 999 + 4997 + 2994, it is easier to regroup each number than to add each digit, one by one.
Think of 999 + 4997 + 2994 as (1000 – 1) + (5000 – 3) + (3000 – 6). Or (1000 + 5000 + 3000) – 1 – 3 – 6. This is the same as (1000 + 5000 + 3000) – (1 + 3 + 6).
We regroup this as 9000 – 10, and the answer is 8990.
Let us try another example. What is 96 + 898 + 697? We regroup this as (100 – 4) + (900 – 2) + (700 – 3).
This is the same as 1700 – 9, so the answer is 1691.
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