Question

Without doing the compotation,explain why or why not 19.7 is a reasonable value for the expression 122.14 divided by 6.2

Answer 1

Rounding 122.14 to the nearest 10 and 6.2 to the nearest whole number gets us the values 120 and 6. Using these estimates for our division gives us the rough result 120 ÷ 6 = 20. 6.2 is a larger number than 6, so division by 6.2 will lower our result, but 122.14 is also bigger than 120, so this increase will raise our result a little as well. The net effect will make the actual quotient come out slightly lower than our estimate of 20, so 19.7 is a perfectly reasonable value.