Repeated subtraction is a way of teaching about division. It is the repeated subtraction of the same number from a large number down to zero. It is a great way to introduce children to division.
Repeated Subtraction is a method that subtracts an equal number of items from a group, also known as division. Also, the same number is subtracted repeatedly from another more significant number until the remainder is zero or more negligible than the number being deducted.
Why is repeated subtraction useful?
Learning about division as repeated subtraction allows children to use a skill they are already familiar with; this gently introduces them to a new concept that might be difficult to understand at first. Because of this, repeated subtraction is especially useful for younger primary children new to the division. It is similar to how repeated addition can be used to teach a lesson on multiplication.
Not only will it make these abstract concepts less daunting, but it will also give them an essential procedure for working out problems related to division.
Repeated subtraction is also a valuable tool for individual learning. For example, when first attempting to solve division problems on your own, having an ordinary skill to fall back on will make the process much simpler.
Examples of Repeated Subtraction
There are two ways repeated subtraction can be used to get the correct answer:
- The first method is where the divisor is subtracted until the remainder is less than the divisor. For example, if you had the question 30 ÷ 6, you would remove 6 from 30 until the rest is less than 6. In this case, after subtracting five times, you would be left with the answer 5.
- The second way to use division as repeated subtraction is to note how many times you subtracted the divisor. For example, in the question above (30 ÷ 6), six were taken away from 30 five times. So the answer you would write here would be 30 ÷ 6 = 6 r5, which translates to 6 with the remainder 5 (or five left over).
Let’s take another example: what is 38 divided by 5? You could use repeated subtraction to find out how many times you could take five away from 34 before hitting a number smaller than 4; this (plus the remainder) would be your answer. For example:
- 38 – 5 = 33
- 33 – 5 = 28
- 28 – 5 = 23
- 23 – 5 = 18
- 18 – 5 = 13
- 13 – 5 = 8
- 8 – 5 = 3
So the answer is 7 with a remainder of 3