Question

A painter is asked to paint the exterior of a dome, excluding the bottom, which has a diameter of 9 ft. The painter already has one gallon of paint which will cover 105 ft2.

How much more paint will the painter have to purchase to complete the job with the least amount of waste, calculated with a precision of 0.00?

Answer 1

Area of the dome is given by:
A=1/2(4πr²)=2πr²
thus:
A=2×3.14×(9/2)²
A=127.17 ft²
Thus the remaining area to be painted will be:
127.17-105
=22.17 ft²

Amount of paint required will be:
22.17/105*1=0.211 gallons
Thus the best approximation is:

A] 1 quart covers 26.25 ft²