Estimating difficult questions
Example 1
Estimate 108+387.348
108 would be best estimated to the tens units to give 110
387.3 would be best estimated to the tens units to give 390
48 would be best rounded to 50
The calculation would then be
110+39050
which equals 50050
which equals 10
The actual answer is 10.32 so we can see that 10 is a useful estimate.
Example 2
Estimate
38.3×50.45.1+4.98
38.3 would be best rounded to 40
50.4 would be best rounded to 50
5.1 would be best rounded to 5
4.98 would also be best rounded to 5
So the calculation becomes
40×505+5
We can work this out as 200010
which equals 200
The actual number is 191.5 so we can see that 200 is a useful estimate.
