# Question #d6001

##### 1 Answer

Two.

#### Explanation:

As you know, **all non-zero digits** are significant, so right from the start, you know that this measurement has at least **significant figures** because it contains two non-zero digits.

#0.00078 " "-> " " "two non-zero digits: " 7,8#

Now, your goal is to figure out if any of the four zeroes are significant.

In this regard, you can use the fact for numbers that are **follow** the decimal point are only significant if they also follow a non-zero digit.

If the zeroes follow the decimal point *directly*, then they are **not** significant.

In your case, you have

#0.00078 < 1#

so you must at the three zeroes that follow the decimal point. Since they do not follow any non-zero digits, you can say that they are **not** significant.

#color(black)(0. color(red)(000)78)" " -> " " "three non-significant zeroes"#

Similarly, for numbers that are *placeholder zero* and is **not** significant.

#color(blue)(0) .color(black)(00078)" " ->" " "a non-significant placeholder zero"#

Therefore, you can say that your measurement has **significant figures**, the non-zero digits.