RULES IN ROUNDING OFF NUMBERS WITH DECIMALS

The number 8.4236 can be rounded to a specified number of decimal places

8.4236 --> 8.424 to 3 decimal places

8.4236 --> 8.42 to 2 decimal places

8.4236 --> 8.4 to 1 decimal place

Problem 1 :

Write each of the following numbers correct to 2 decimal places.

Solution :

a) 4.263

• Underline the 2nd digit after the decimal. 4.263
• Look at the 3^rd digit after the decimal.
• 3^rd digit is 3 which is less than 5.
• There is no change in the underlined digit.
• So, the answer is 4.26.

b)  0.0472

• Underline the 2nd digit after the decimal. 0.0472
• Look at the 3^rd digit after the decimal.
• 3^rd digit is 7 which is greater than 5.
• Add 1 with the underlined digit.
• So, the answer is 0.05

c)  10.8374

• Underline the 2nd digit after the decimal. 10.8374
• Look at the 3^rd digit after the decimal.
• 3^rd digit is 7 which is greater than 5.
• Add 1 with the underlined digit.
• So, the answer is 10.84.

d)  82.062

• Underline the 2nd digit after the decimal. 82.062
• Look at the 3^rd digit after the decimal.
• 3^rd digit is 2 which is lesser than 5.
• There is no change in the underlined digit. 
• So, the answer is 82.06

e)  3.445

• Underline the 2nd digit after the decimal. 3.445
• Look at the 3^rd digit after the decimal.
• 3^rd digit is 5 which is lesser than 5.
• Add 1 with the underlined digit.
• So, the answer is 3.45.

f)  9.395

• Underline the 2nd digit after the decimal. 9.395
• Look at the 3^rd digit after the decimal.
• 3^rd digit is 5.
• Add 1 with the underlined digit.
• So, the answer is 9.40

g) 6.254

• Underline the 2nd digit after the decimal. 9.395
• Look at the 3^rd digit after the decimal.
• 3^rd digit is 5.
• Add 1 with the underlined digit.
• So, the answer is 9.40

h)  3.216

• Underline the 2nd digit after the decimal. 3.216
• Look at the 3^rd digit after the decimal.
• 3^rd digit is 6. Which is greater than 5.
• Add 1 with the underlined digit.
• So, the answer is 3.22.

Problem 2 :

Write the number 8.645712 correct to 

a) 3 decimal places 

b) 4 decimal places

c) 1 decimal place

Solution :

Given number is 8.645712

a) 3 decimal places 

• Underline the 3rd digit after the decimal. 8.645712
• Look at the 4^th digit after the decimal.
• 4^th digit is 7. Which is greater than 5.
• Add 1 with the underlined digit.
• So, the answer is 8.646

b) 4 decimal places

• Underline the 4th digit after the decimal. 8.645712
• Look at the 5^th digit after the decimal.
• 5^th digit is 1. Which is lesser than 5.
• No change in the underlined digit.
• So, the answer is 8.6457

c) 1 decimal place

• Underline the 1^st digit after the decimal. 8.645712
• Look at the 2^nd digit after the decimal.
• 2^nd digit is 4. Which is lesser than 5
• No change in the underlined digit.
• So, the answer is 8.6

Problem 3 :

Write the number 183.9591 correct to.

a) 3 decimal places

b)  3 significant figures

c)  5 significant figures

d)  3 significant figures

e)  1 decimal place

Solution :

183.9591

a) 3 decimal places

183.9591

• Underline the 3^rd digit after the decimal. 183.9591
• Look at the 4^th digit after the decimal.
• 4^th digit is 1. Which is lesser than 5
• No change in the underlined digit.
• So, the answer is 183.959

b)  3 significant figures

183.9591

• Look at the 4^th digit
• 4^th digit is 9. Which is greater than 5
• We add 1 with the 3, then
• the answer is 184

c)  5 significant figures

183.9591

• Look at the 6^th digit
• 6^th digit is 9. Which is greater than 5
• We add 1 with the 5, then
• the answer is 183.96

d) 1 decimal place

183.9591

• Look at the 2^nd digit
• 2^nd digit is 5.
• We add 1 with the 9, then
• the answer is 184.0