Question

What is the sum of 2.7 g and 2.47g expressed in the correct number of significant digits

Answer 1

Answer :  The answer will be, 5.2 g

Explanation :

Significant figures : The figures in a number which express the value -the magnitude of a quantity to a specific degree of accuracy is known as significant digits.

The rule apply for the addition and subtraction is :

The least precise number present after the decimal point determines the number of significant figures in the answer.

As we are given that the sum of 2.7 g and 2.47 g.

$2.7g+2.47g$

$\Rightarrow 5.17g$

In the given expression, 2.7 has 2 significant figures and 2.47 has 2 significant figures. From this we conclude that least precise number present after the decimal point is 1.

Thus, the answer will be $\Rightarrow 5.2g$

Answer 2

In order to get the sum of 2.7 and 2.47, we will add both numbers. So, 2.7 plus 2.47 would be 5.17. And the correct number of significant digits in this number is still the same, 5.17, so we have three significant numbers. Why? There are three rules in identifying the significant figures: 1. Non zeros are always significant (which this applies in our sum above). 2. Any zeros in between significant numbers are always significant. 3.  The final zero or zeros in the decimal portion only are significant.