... an estimated sum or difference of proper fractions based on rounding to nearest 1/2,1/4 or 1/8. Fractions, n/d, where n < d and 0 <= n/d <= 1. ... Fractions are rounded to 0,1/2 or 1. ... Estimating sums and differences of fractions to the nearest 1/2 ... Therefore, you should use good judgment in your estimating process.
