Please tell me the answer

The circumference of a redwood tree trunk is 20π ft, and it is 100 ft tall. what is the approximate volume of the redwood tree trunk? 1,000π ft3 10,000π ft3 4,000π ft3 40,000π ft3

Anyone? 15m is what percent of 60m; 3m; 30m; 1.5 km?

The difference of three and the reciprocal of a number is equal to the quotient of 20 and the number. find the number.