Question

Add and subtract with scientific notation $1,99 \times 10^{-26}+1,67 \times 10^{-27}-2,79 \times 10^{-25}=?$

Answer 1

Step 1: Make all the exponents the same To add or subtract numbers in scientific notation we must make all the exponents the same:

$$

\begin{array}{l}

1,99 \times 10^{-26}=0,199 \times 10^{-25} \text { and } \\

1,67 \times 10^{-27}=0,0167 \times 10^{-25}

\end{array}

$$

Step 2 : Carry out the addition and subtraction Now that the exponents are the same we can simply add or subtract the $N$ part of each number:

$$

0,199+0,0167-2,79=-2,5743

$$

Step 3: Write the final answer To get the final answer we put the common exponent back:

$$-2,5743 \times 10^{-25}$$