Answer:
0.4 lawns per hour
Explanation:
We are asked how long it would take on average to mow all the lawn per hour.
We are told that you can mow half a lawn in 1 1/4 hours, that is to say in 1.25 hours, which means that to mow the lawn completely it must have an average of twice the time, that is:
1.25 * 2 = 2.5
Which means that on average it takes 2.5 hours to mow all the lawn.
1/2.5 = 0.4 lawns per hour