How to correct to 3 significant figures to these values

a) 20.961

b) 0.275

c) 15.62 and 3.555 ... ?

The significant figures of a number are digits that carry meaning contributing to its measurement resolution. The correct 3significant figures to these values would be

a) 20.961 = 21.0

b) 0.275 = 0.275

c) 15.62 = 15.6

d) 3.555 = 3.56