Can someone pls pls help

Does the point (1, sqrt 7) lie on circle shown.

Abicycle training wheel has a radius of 3 inches. the bicycle wheel has a radius of 10 inches. approximately how much smaller, in square inches and rounded to the nearest hundredth, is the area of the training wheel than the area of the regular wheel? *

Which equation can be used to measure the density of water in a spherical water tank? let w represent the number of water particles within the region.