# Question #b65fe

##### 1 Answer

Since no additional information was provided, I'll treat this an a significant figures problem, since that's the only way this question can make sense.

Let's say you have to add a number to 0.259 in order to get 0.51. Here's how you'd go about doing that.

Notice that you need to go from a number that has *3 significant figures* to a number that has *2 significant figures*. The only way to do that and get the values given is to **add** a number that has only 2 significant digits, both **after the decimal**, to the first number.

When you add or subtract *decimal numbers*, you go by the number of sig figs that are **after the decimal** only.

If you subtract **0.259** from **0.51**, you'll get

Notice that the answer has 3 sig figs after the decimal: 2, 5, and 1.

This means that you have to round this number off to only 2 sig figs after the decimal, which will give you **0.25**.

Now, if you add **0.25** to **0.259**, you'll get

Rounded to 2 sig figs after the decimal, the answer will be