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Division

lesson · about 3 minutes

Division as a missing factor, then bigger exact divisions.

Best in your head · no pen, no calculator why?

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the idea

Division undoes multiplication. 56 ÷ 8 asks: 8 times what makes 56? So every times-table fact you know is also a division fact.

Bigger divisions come down to small ones. You can cross the same zeros off both numbers, or split a big number into pieces that divide cleanly.

Dividing by a number below 1 makes the answer bigger. 10 ÷ 0.5 asks how many halves fit in 10, and there are 20 of them.

techniques

Missing factor, then zeros

Any exact division, including numbers that end in zeros.

  1. Read 56 ÷ 8 as 8 × ? = 56. The missing factor is the answer.
  2. If both numbers end in zeros, cross the same number of zeros off each.
  3. Find the fact that fits the front digits. In 3,000 ÷ 6, that is 30 ÷ 6 = 5.
  4. Each zero after those digits goes on the end of the answer: 500.
worked example

Example: 3,500 ÷ 70

  1. Cross one zero off each: 350 ÷ 7.
  2. 35 ÷ 7 = 5, and one zero is left: 50.

Answer: 50

Split the number into pieces

Dividing by 6 to 15 when the answer is between 10 and 30.

  1. Take out 10 lots of the divisor, or 20 lots if that still fits.
  2. Divide what is left with a fact.
  3. Add the two answers.
worked example

Example: 195 ÷ 13

  1. 10 × 13 = 130, so split 195 into 130 + 65.
  2. 130 ÷ 13 = 10, and 65 ÷ 13 = 5.
  3. 10 + 5 = 15.

Answer: 15

more: Split and combine

Count halves and quarters

Dividing by 0.5 or 0.25.

  1. ÷ 0.5 asks how many halves fit. Each whole holds 2, so double the number.
  2. ÷ 0.25 asks how many quarters fit. Each whole holds 4, so multiply by 4.
  3. Check the size: the answer is bigger than the number you started with.
worked example

Example: 13 ÷ 0.25

  1. Each whole holds 4 quarters.
  2. 13 × 4 = 52.

Answer: 52

watch out for

practice

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Division facts

worked example

16 ÷ 8

Answer: 2

  1. Read it as a missing factor: 8 × ? = 16. Since 8 × 2 = 16, the answer is 2.

Divide with zeros

worked example

120 ÷ 60

Answer: 2

  1. Cancel a zero from both numbers: 120 ÷ 60 = 12 ÷ 6.
  2. 12 ÷ 6 = 2, because 6 × 2 = 12.

Split the dividend

worked example

225 ÷ 15

Answer: 15

  1. Split 225 into 150 + 75.
  2. 150 ÷ 15 = 10 and 75 ÷ 15 = 5, so the answer is 15.

÷ 0.5 and ÷ 0.25

worked example

35 ÷ 0.25

Answer: 140

  1. Dividing by 0.25 asks how many quarters fit. Each whole holds 4 quarters, so 35 × 4 = 140.

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