Division Using multiplication and repeated subtraction Whats It

Division Using multiplication and repeated subtraction

What’s It All About? You are going to learn: How to divide by inversing multiplication and using repeated subtraction. What skills should you have already? You need to be able to multiply and subtract two values using a written method.

Division Remember that 6 ÷ 3 means “how many threes make 6? ” Division is the INVERSE of Multiplication. There are different ways of showing division. 6÷ 3 The answer is the same in all three cases!

Using Multiplying to Divide For multiplying, we can use a grid like this: 2 3 4 1 2 3 4 2 4 6 8 3 4 5 6 7 8 9 6 8 10 12 14 16 18 9 12 15 18 21 24 27 12 16 20 24 28 32 36 5 6 10 15 20 25 30 35 40 45 12 18 24 30 36 42 48 54 We can now use it to divide as well as multiply. Example: 20 4 means “How many 4’s make 20? ” The answer is 5.

Your Turn Remember that 6 ÷ 3 means “how many threes make 6? ” Work out: 1. 16 ÷ 4 2. 30 ÷ 5 3. 30 ÷ 10 4. 45 ÷ 9 5. 72 ÷ 8 6. 21 ÷ 3 7. 21 ÷ 7

Repeated Subtraction 1 Work out £ 192 ÷ 6 Set up the method: 6 192 60 132 60 72 60 12 12 0 £ 192 6 = 32 10 10 10 2 32 Multiply 6 by something easy such as 10 or 100, then subtract. Repeat this until you have nothing left or the number that is left is less than 6. Stop. Total up the 6’s.

Repeated Subtraction 2 Work out £ 324 ÷ 12 Set up the method: 12 324 120 204 120 84 60 24 24 0 10 10 5 2 27 £ 324 12 = 27 Multiply 12 by something easy such as 10 or 100, then subtract. Repeat this until you have nothing left or the number that is left is less than 12. Stop. Total up the 12’s.

Repeated Subtraction 3 Work out £ 3010 ÷ 14 Set up the method: 14 3010 1400 1610 1400 210 140 70 70 0 100 10 5 215 £ 3010 14 = 215 Choosing sensible numbers reduces the amount of subtracting you have to do. . Multiply 14 by something easy such as 10 or 100, then subtract. Repeat this until you have nothing left or the number that is left is less than 14. Stop. Total up the 14’s.

Your Turn Remember that 6 ÷ 3 means “how many threes make 6? ” Work out: 1. 164 ÷ 4 5. 156 ÷ 12 2. 305 ÷ 5 6. 315 ÷ 15 3. 3040 ÷ 10 7. 3040 ÷ 20 4. 4509 ÷ 9 8. 2814 ÷ 14

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