Estimating using compatible numbers

With experience, you should start to recognise easy multiples and division numbers.

Our friends say we are not compatible but are easily recognised.

Example 1

Estimate the division of `2391div11.9`

Diving `2391` by `11.9` is very difficult

but `2400/12` is very easy

`2400/12=200`

NOTE:

The real answer is `200.92` so you can see our estimation was very close.

Example 2

Estimate the division of `2095div3`

Diving `2095` by `3` is very difficult

but `2100/3` is very easy

`2100/3=700`

NOTE:

The real answer is `698.33` so you can see our estimation was very close.

Example 3

Estimate the multiplication of `27times43`

Multiplying `27times43` is difficult

but `25times40` is easy

`25times40=1000`

NOTE:

The real answer is `1,161` which is a little bit higher but `1000` is a suitable guide.

Example 4

Estimate the division of `55764div825`

Dividing `55764` by `825` is very difficult

but `56000/800` is easy

`(560cancel0cancel0)/(8cancel0cancel0)=70`

NOTE:

The real answer is `67.59` and so `70` is an apt estimate.