Answer :
Answer : The answer in standard form is, 0.00318 mg.
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 :
[tex](3.26\times10^{-3})mg-(7.88\times 10^{-5})mg[/tex]
First we have to convert scientific notation into standard form.
[tex]\Rightarrow 0.00326mg-0.0000788mg[/tex]
[tex]\Rightarrow 0.00318mg[/tex]
As per rule, the least precise number present after the decimal point is 5. So, the answer will be, 0.00318 mg.