When evaluating complicated expressions, we (humans) tend to make errors. We miss decimal points, forget a minus sign, etc. Estimating roughly what value to expect from a series of calculation helps us compare with our laboriously calculated exact solution.
If the estimate and the exact result are far off we know we must have made a mistake.
Estimating is a skill that is important by different ways like: decimal places, rounding, and probability percentages. This help you get a reasonable check by confirming or verifying your answer into accuracy. Estimating a problem would be helpful to towards you and your answering ability.
The area of square part of arch is 10*10=100 the diameter of the circle is 10 therefor radius is 5 and area is \[\pi*r^2=\pi*25\] therefore total area is 100+25pi </span>
