Find the value of the variable using Square Root Equations

Question

The radius r (in inches) of a ball is given by r=✔️S/4π ( under the radical), where S is the surface area (in square inches) of the ball. Use the trace feature of a graphing calculator to find the least whole number value of S at which the radius exceeds 5 inches.

Answer 1

r=✔️S/4π

5<(√s)/4*π

1.591...<(√s)/4

6.366...<√s

40.528...<s

Answer 2

sqrt(S/4π) = r

sqrt(S/4π) > 5

S/4π > 25

S > 100π ≈ 314.16 in²

The surface area should be at least 315 square inches.