Question

(need answer asap) The histogram shows the time (secs) it took members at a swimming club to
swim the length of the pool.
Given that 10 people swam it in 20 seconds or less, estimate the fraction of
members who took longer than 42 seconds.

Answer 1

Estimate that the range of 10-20 seconds is 2x taller but 2x thinner than 20-30 seconds.

So, the range from 10-20 is equal to 20-30 (just an estimate)
And we also can estimate 20-30 is equal to 30-40 (as we can't know how much thinner it is.)

From 40-50, it is 2x shorter than 30-40, so we can also estimate that it is 2x less than 30-40. (and 50-60 equal 40-50)

From 70-80 and 80-90, let's say it's 4/5 40-50 and 50-60

So, taking 10-20 as the fixed amount, the total fraction is 1 + 1 + 1 + 1/2 + 1/2 + 4/5 + 4/5 = 28/5.

40-42 is 2/5 40-45.

So, estimate that the fraction of members who took longer than 42 seconds is 28/5 - 1 - 1 - 1 - 2/5 = 11/5.