A chemist needs to know the mass of a sample of to significant digits. She puts the sample on a digital scale. This is what the scale shows: 0 0 7 6 . 2 1 g If this measurement is precise enough for the chemist, round it to significant digits. Otherwise, press the "No solution" button.

In any type of scientific measurement, the precision of the measurement is expressed in the significant digits of that measurement. It also used to express measurement to the required degree of accuracy.

Significant digits include every digit except the leading zero(s).

And if the number after the required significant digits is not up to 5, it is rounded down and the required significant digits is written as is. But if the number after the required significant digits is at least 5, it rounded up, and the last number on the significant digits requirement is increased by a factor of 1.

Examples include

0.3547 = 0.355 to 3 s.f (0.0007 is rounded up to increase the next digit, 4, by a factor of 1)

7.399 = 0.40 to 2 s.f

Hence, the given mass, 76.21 g becomes 76 g to 2 significant figures since the next digit after the required significant digits, 2, is less than 5, it is rounded down.

76.21 = 76.2 to 3 s.f

76.21 = 76 to 2 s.f

76.21 = 80 to 1 s.f

I hope you get it now!