Circletown's limits form a perfectly circular shape. It has a population of 20,000 and a population density of 480 people per square kilometer. What is Circletown's radius?

Can someone check if i did this correct. it’s number 4 if you’re wondering.

According to a study conducted in 2015, 18% of shoppers said that they prefer to buy generic instead of name-brand products. suppose that in a recent sample of 1500 shoppers, 315 stated that they prefer to buy generic instead of name-brand products. at a 5% significance level, can you conclude that the proportion of all shoppers who currently prefer to buy generic instead of name-brand products is higher than .18? use both the p-value and the critical-value approaches.

There are a total of 75 students in the robotics club and science club. the science club has 9 more students than the robotics club. how many students are in the science club?