It will take 30 minutes more for remaining grass.
As he mowed 40% in 20 minutes, it shows that he mows twice percentage of grass in the time calculated in minutes.
So it will take 30 minutes for remaining 60% grass.
well let's round. 90= 100, 75=80 that is how I face it. now 80 is 1/5 of 5/5= 100. so as a (%) we would sort it like:::: it is 80% out of +100 so he must have grown around 13%-16% due to him being 75kg in the past.
