Q.Why there is a need of rounding off figures during calculation ?

When several measured quantities of differing precision are combined in a calculation, the accuracy of the final result can never exceed the accuracy of the LEAST accurate (fewest-significant-figure) measurement used — a calculation cannot manufacture precision that was not present in its inputs. Because raw calculated results routinely contain more digits than are actually justified, they must be rounded off to the appropriate number of significant figures before being reported, using a simple two-part rule: if the digit right after the last digit being kept is less than 5, the kept digit is left unchanged; if that following digit is 5 or more, the kept digit is increased by …