# Suppose you add a measurement of 7.2 mL to a measurement of 15.37 mL. How many decimal places should the answer have?

Aug 20, 2016

The answer must have $1$ decimal place.

#### Explanation:

The thing to remember when dealing with addition or subtraction is that the result must be rounded to the same number of decimal places as the measurement with the least number of decimal places.

In your case, you have two measurements, $\text{7.2 mL}$, which is rounded to one decimal place, and $\text{15.37 mL}$, which is rounded to two decimal places.

This means that the value you get by adding these two measurements must be rounded to one decimal place.

So, add the two measurements to get

$\text{7.2 mL " + " 15.37 mL" = "22.57 mL}$

Now, this number, $22.57$, must be rounded to the tenths place, i.e. to one decimal place. You will thus have

$22.5 \textcolor{red}{\cancel{\textcolor{b l a c k}{7}}} \implies 22.6$

$\textcolor{g r e e n}{| \overline{\underline{\textcolor{w h i t e}{\frac{a}{a}} \textcolor{b l a c k}{\text{7.2 mL " + " 15.37 mL" = "22.6 mL}} \textcolor{w h i t e}{\frac{a}{a}} |}}}$