Page 47 - Mathematics

Rounding off numbers by place values
Rounding off numbers by place values is done by considering the given place value
for both whole and decimal parts of a number. Thus, for whole numbers, it can be
done to the nearest ones, tens, hundreds, thousands or any other place value. For
decimal numbers, it can be done to the nearest tenths, hundredths, thousandths and
so on. The following are basic procedures for rounding off numbers by place values. Tanzania Institute of Education
(a) If the digit to the right of the rounding digit is either 0, 1, 2, 3, or 4, then the
digit at the required place value remains unchanged, and each digit to the right
of it become zeros.

Note:
A rounding digit is the digit at a place where a number is supposed to be
rounded off.

Example 3.1

Round off each of the following numbers according to the given instruction.
(i) 591,622 to the nearest hundreds.
(ii) 35.4 to the nearest ones.
(iii) 234 to the nearest hundreds.

Solution
(i) The digit of 591,622 in the hundreds place is 6 and the digit on the right
of 6 is 2, which is less than 5. In this case, maintain 6 and replace each
digit to the right of 6 with zero. Thus, 591,622 to the nearest hundreds
is 591,600.
(ii) 35.4 to the nearest ones is 35.
(iii) 234 to the nearest hundreds is 200.

Example 3.2

Round off;
(i) 35.49643 to the nearest thousandths.
(ii) 274 to the nearest tens. Mathematics Form One
(iii) 3.2743 to the nearest hundredths.
(iv) 856,145 to the nearest thousands.
(v) 42.245468 to the nearest thousandths.

41

25/10/2024 09:51:12
Mathematics form 1.indd 41
Mathematics form 1.indd 41 25/10/2024 09:51:12