 # 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.