We know that 1 in = 2.54 cm
From this equivalence, we can write
`(1"in ")/(2.54 cm ) =1=(2.54 cm )/(1 "in ")`
thus ,`(1 "in")/(2.54 cm) `equals 1 and `(2.54 cm) /(1 "in")` also equals 1. Both of these are called unit factors. If some number is multiplied by these unit factors (i.e., 1), it will not be affected otherwise.
Say, the 3 in given above is multiplied by the unit factor. So,
3 in 3 in `xx(2.54 cm) /(1 "in")= 3xx 2.54 cm = 7.62 cm` Now , the unit factor by which multiplication to is to done is that unit factor `((2.54 cm )/(1"in")` in the above case) which gives the desired units i.e., the numerator should have that part which is required in the desired result.
It should also be noted in the above example that units can be handled just like other numerical part. It can be cancelled, divided, multiplied, squared, etc. Let us study one more example.
