Question

iv) 18.238 is round off to four significant figures as
18.20 b) 18.23 C) 18.2360 d) 18.24​

Answer 1

18.238 is round off to four significant figures as (d) 18.24

Let us see what is rounding off of numbers,

Rounding off - Rounding off is the type of approximation. For example - 0.29 can be written as 0.3, 4.567 can be written as 4.57

How to round off decimals?

• In decimals, Identify the rounding off digit and then look at its righthand side.

• If the digit at the righthand side is less than 5, consider it as zero.

• If the digit at the righthand side is greater than or equal to 5, add +1 to the digit.

Answer 2

d. 18.24 is the correct round off with four significant figures.  

The most significant digit is the left most digit (excluding zeroes). Here it is 1. If the number is being rounded to 4 digits (n=4) then the digit which is the least significant one is 3 . The first digit which is not significant is the  (n+1=5) $5^{th}$digit i.e 8.

Rules of rounding off are :

• If the first digit which is not significant is less than five , the answer is unchanged.

• If the first digit which is not significant is greater than five , the answer is raised by one.

• If the first digit which is not significant is five , the the number is raised by one or unchanged.

• Therfore, in the number 18.238, 8 is greater than 5 and the number before it is raised by one i.e 18.24.