What the uses of rounding numbers?

Answer 1

• Some measures simply do not make sense unless they are rounded. A common example is currency. There is little point in stating that 5% of 47 cents is 2.35 cents since such a sum does not exist. Or consider a school trip for 110 children where each bus takes 40 children. Will you hire 2.75 buses? No, you will round up to 3 buses because you cannot get 0.75 of a bus!

• Some numbers cannot be written out in full. For example, 1/13 = 0.0769230769... All Irrational Numbers would fall into this category.

• Excessive accuracy (absence of rounding) makes for much more complicated calculation with little, if any improvement in accuracy of the result. For example, the value of pi is known to over 10 trillion digits (as of Sept 2012). But , the value to only 39 decimal places is enough to give a measure of the circumference of the known universe that is accuracy to the diameter of a hydrogen atom. For most normal uses 5 dp (3.14159) is sufficient.