To find where the decimal point should be placed in the product, count the number of digits to the right of the decimal places in both numbers. To check your answer with estimation, round each decimal to the nearest ones place by asking yourself if the number to the right of that place is less than five or five or greater. If the former is true, move the number in the ones place down once. If the latter is true, move the number in the ones place up once. In the case of 25.5 x 0.81, the problem rounded would be 26 x 1, which equals 26. So, we could say that
25.5 x 0.81 = about 26.
(The actual answer is 20.655, by the way.)
