What is 121 rounding to the nearest 100 and what is 252 rounding to the nearest 100

Pls , the question is in the picture!

Which is a reasonable estimate of the amount of water in a small, inflatable pool used by children?

Two cyclists 84 miles apart start riding toward each other at the samen time. one cycles 2 times as fast as the other. if they meet 4 hours later what is the speed (in miles) of the faster cyclists