Question

Subtract 0.2J from 7.26J and express the result with the correct number of significant figures.
A. 7.1J
B. 7.06J
C. 7.0J
D. 7J

Answer 1

Hint: The term significant figure is defined as the number of important single digits (from 0 to 9) in the coefficient of an expression in scientific notation. The number of significant figures is also an expression that indicates the confidence or precision with which an engineer or scientist states a quantity.

Complete step by step solution:
There is a rule in order to solve this problem, that while doing addition, or subtraction, the final result should retain as many decimal places as there are in the number with the least decimal places. According to this, we can write it as,
\[7.26 - 0.2 = 7.06\,J \\ \]
Here the least number is 0.2. and the number of significant figures in the decimal portion that is to the right of the decimal point is 0. Hence the answer should have 1 figure after the decimal point. Hence the answer is 7.1 J. or rounding off this value to 1 decimal place.
So, the final result =7.1J
Therefore, the result with the correct number of significant figures is 7.1 J.

Hence, option A is the correct answer.

Additional information: These significant figures are used to establish the number which is presented in the form of digits and these carry a meaningful representation of numbers. The significant digits are also used often instead of figures. We can find the number of significant digits by counting all the values starting from the first non-zero digit located on the left.

Note: In this problem it is important to remember when we are going to find the significant figures. We need to count the digits in such a way that, if a number contains zero in the starting, we have to eliminate it. We have to count when in the given question if the zeros are present in the middle of the number.