Five people can mow a lawn in 12 hours. how many more people are needed to mow the lawn in just 3 hours, assuming each person mows at the same rate?

The number of people mowing and the time required to mow are inversely proportional. Letting n be the number of people and t be the amount of time, we have nt = (5)(12)= 60 because 5 people can mow a lawn in 12 hours. If m people can mow the lawn in 3 hours, then we must have m(3) = 60, so m=20. Therefore, we need to add 20-5 = 15 people to the job.