There is a reservoir with five channels that fill it at different rates: channel 1 fills it in 1/3 day, channel 2 in 1 day, channel 3 in 2.5 days, channel 4 in 3 days, and channel 5 in 5 days. The problem asks how long it would take for the reservoir to fill if all five channels were open simultaneously. The solution calculates the fill rate of each channel in reservoir units per day, sums these rates, and takes the reciprocal to find the time in days to fill the reservoir is 0.202 days.