Introduction to rules on rounding off of decimal in maths:
To round a number to a certain number of decimal places, proceed as under
(i) Work out the number to one more place than you need.
(ii) If the extra digit is 5 or more, add 1 to the number before it.
(iii) If he extra digit is less than 5, leave the number before it as it is,
Look at the following examples and make sure that I have rounded them correctly:
49·3795 = 49·4 correct to one decimal place
49·3795 = 49·38 correct to two decimal places
7·2485 = 7·249 correct to three decimal places
7·2485 = 7·25 correct to two decimal place
7·2485 = 7·2 correct to one decimal place
0·0536 = 0·1 correct to one decimal place
0·0536 = 0·05 correct to two decimal places
0·0536 = 0·054 correct to three decimal places
2·397 = 2·40 correct to two decimal places
Examples on Rounding off of Decimas in Math:
Round off:
(i) 6.5347, correct to 2 decimal places
(ii) 12.3415, correct to 3 decimal places
(iii) 4.863, correct to 1 decimal place
Sol:
(i) We retain 2 digits of to digits of he decimal part n 6.5347 to get 6.53 and omit the digits 4 and 7.
The first omitted digit is 4 < 5
So, we do not make a change in retained digits
... Required number = 6.53
(ii) We retain 3 digits of the decimal part in 12.3415 to get 12.341 and omit the digit 5.
Since the first omitted digit is 5, we in crease the last retained digits by 1, i.e., make it 2.
... Required number = 12.342
(iii) We retain 1 digit of the decimal part in 4.863 to get 4.8 and omit the digits 6 and 3.
The first omitted digit is 6 > 5
So, we increase the last retained digit by 1, i.e., make it 9.
... Required number = 4.9
Note:-
(i) To the nearest tenths means correct to 1 decimal place
(ii) To the nearest hundredths means correct to 2 decimal places
(iii) To the nearest thousandths means correct to 3 decimal places and so on
More Examples on Rounding off of Decimals in Math:
Round off
(i) 4.1234 to the nearest tenths
(ii) 127.42851 to the nearest thousandths
Solution
(i) We have to round off 4.1234 correct to 1 decimal place
We retain 4.1 and omit the digits 2, 3 and 4
The first omitted digit is 2 < 5
So, we do not make a change in the retained digits
... Required number = 4.1
(ii) We have to round off 127.42851 correct to 3 decimal places
We retain 127.428 and omit the digits 5 and 1
The first omitted digit is 5
So, we increase the last retained digit by 1.
... Required number = 127.429
To round a number to a certain number of decimal places, proceed as under
(i) Work out the number to one more place than you need.
(ii) If the extra digit is 5 or more, add 1 to the number before it.
(iii) If he extra digit is less than 5, leave the number before it as it is,
Look at the following examples and make sure that I have rounded them correctly:
49·3795 = 49·4 correct to one decimal place
49·3795 = 49·38 correct to two decimal places
7·2485 = 7·249 correct to three decimal places
7·2485 = 7·25 correct to two decimal place
7·2485 = 7·2 correct to one decimal place
0·0536 = 0·1 correct to one decimal place
0·0536 = 0·05 correct to two decimal places
0·0536 = 0·054 correct to three decimal places
2·397 = 2·40 correct to two decimal places
Examples on Rounding off of Decimas in Math:
Round off:
(i) 6.5347, correct to 2 decimal places
(ii) 12.3415, correct to 3 decimal places
(iii) 4.863, correct to 1 decimal place
Sol:
(i) We retain 2 digits of to digits of he decimal part n 6.5347 to get 6.53 and omit the digits 4 and 7.
The first omitted digit is 4 < 5
So, we do not make a change in retained digits
... Required number = 6.53
(ii) We retain 3 digits of the decimal part in 12.3415 to get 12.341 and omit the digit 5.
Since the first omitted digit is 5, we in crease the last retained digits by 1, i.e., make it 2.
... Required number = 12.342
(iii) We retain 1 digit of the decimal part in 4.863 to get 4.8 and omit the digits 6 and 3.
The first omitted digit is 6 > 5
So, we increase the last retained digit by 1, i.e., make it 9.
... Required number = 4.9
Note:-
(i) To the nearest tenths means correct to 1 decimal place
(ii) To the nearest hundredths means correct to 2 decimal places
(iii) To the nearest thousandths means correct to 3 decimal places and so on
More Examples on Rounding off of Decimals in Math:
Round off
(i) 4.1234 to the nearest tenths
(ii) 127.42851 to the nearest thousandths
Solution
(i) We have to round off 4.1234 correct to 1 decimal place
We retain 4.1 and omit the digits 2, 3 and 4
The first omitted digit is 2 < 5
So, we do not make a change in the retained digits
... Required number = 4.1
(ii) We have to round off 127.42851 correct to 3 decimal places
We retain 127.428 and omit the digits 5 and 1
The first omitted digit is 5
So, we increase the last retained digit by 1.
... Required number = 127.429
