Rounding Numbers and Estimating Answers
Rounding numbers:
In order to round a number to a given decimal place,
1. Note the decimal place in which the rounding is to occur.
2. Locate the digit just to the right of that place.
3. If that digit is less than 5, replace it and all digits to the right of it with
zeros.
4. If that digit is 5 or greater, replace it and all digits to the right of it
with zeros and then add 1 to the digit in the â€œrounding placeâ€.
Ex: Round to the requested place.
a. 2345 to the nearest ten.
b. 2345 to the nearest hundred.
c. 23,954 to the nearest hundred.
Rules for rounding in calculations:
When you are completing a calculation
and are asked to round your answer, do all calculations first without
rounding and then round your final answer.
Ex: Multiply and round to the nearest hundred.
235(446)
Estimating:
When estimating the answer to a calculation, use rounded
numbers to do the arithmetic. You donâ€™t need to round your answer.
Ex: Estimate to the nearest ten the sum of the three numbers 435, 761 and
997.
