The approximations used in estimating numbers are compounded when calculations are done with those numbers. For instance, if we know that a = 5.2 to one decimal place and b = 1.3 to one decimal place, then the range for the sum c=a+b can be from 5.15+1.25 through to 5.25+1.35, i.e. 6.4 ⩽ c < 6.6.
Example
If a = 3.6 to 1 decimal place and b = 14 to the nearest whole number, find the upper and lower bounds for each of the following:
(a.) a+b (b.) ab (c.) b – a (d) a/b (e) (a+b)/a
Exercise
Answers
Maths with David 