Adding and subtracting to a million · Grade 4
In Adding and subtracting to a million (Grade 4) you practise 4 skills: Column addition and subtraction · Clever strategies · Equations and inequalities · Estimating. In an addition you can take an amount from one number and add the same amount to the other, and the sum does not change. So 3,625 + 1,297 equals 3,622 + 1,300, and the second one is easy to work out in your head.
In a subtraction you can add the same amount to both numbers, or take the same amount from both, and the difference does not change. So 5,000 − 1,998 equals 5,002 − 2,000, which is 3,002. Addition and subtraction undo each other. Use them to check an answer and to find a missing number: if ☐ + 2,500 = 7,000, the missing number is 7,000 − 2,500, which is 4,500.
Tip: Before you work it out, estimate: round the numbers, and at the end check that your answer is close to the estimate.
What you learn
Column addition and subtraction
For example: Work out: 861 + 137
Answer and solution
The answer: 998
Write the numbers one under the other, units under units, and work column by column from the right: 861
+ 137
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998 861 + 137 = 998
Clever strategies
For example: Complete it so that both sides are equal: 57,094 + 6,398 = 57,092 + ☐
Answer and solution
The answer: 6400
We took 2 from the first number and added 2 to the second; the sum did not change: 57,092 + 6,400 = 63,492
Equations and inequalities
For example: Find the missing number: 57,100 + ☐ = 63,100
Answer and solution
The answer: 6000
To find a missing number in a sum, take the known number from the total: 63,100 − 57,100 = 6,000 . Check: 57,100 + 6,000 = 63,100
Estimating
For example: Round 2,288 to the nearest thousand.
Answer and solution
The answer: 2000
The deciding digit is 2, so round down: 2,288 ≈ 2,000
The exercises are made by rules and the answers are worked out in code, so there are new exercises every time. The topic follows the new Israeli elementary programme (2023).