Help my brother please it’s test please

The circumference of a circle is 5 pi cm. what is the area of the circle?

An an average person has 6×10 by the power of two as many red blood cells as white blood cells a small sample of the blood has 7×10 by the power of three white blood cells about how many red blood cells are in the sample

Answer asap ! the shortest path from point a to point b goes through a pond. to avoid the pond, you must walk straight 34 meters along one edge of the pond, then take a 90 degree turn, and again walk straight 41 meters along another edge of the pond to reach point b. about how many meters would be saved if it were possible to walk through the pond? a. 11 m b. 20 m c. 30.45 m d. 21.73 m