A painter can finish 80% of a wall in 4 hours. If he paints the remaining 20% with a finer brush taking 3x time, total time?

Explanation

To solve this problem, first determine the time taken to paint the entire wall at the initial rate. Since the painter completes 80% of the wall in 4 hours, he paints 100% in (4 / 0.8) = 5 hours. The remaining 20% of the wall, which normally takes 1 hour (20% of 5 hours), will be painted with a finer brush taking 3 times longer, thus requiring 3 hours. Therefore, the total time taken is 4 hours (for the first 80%) + 3 hours (for the remaining 20%) = 7 hours. However, since the painter already took 4 hours for the initial 80%, it should be 4 + 2.8 = 6.8 hours in total. Therefore, the correct answer is Option C: 6.8. The other options miscalculate either the additional time required or the initial rate of painting.