Hi guys, there's a question in my practice papers

Time (m) minutes Frequency F.D.

0<20 20 1

20<30 30 3

30<40 45 4.5

40<60 60 3

60<100 48 1.2

I did the sum of f/2 +0.5 to get the median value and worked out that 0 to 40 is 95

The answer book then says 40-60:6.5/60*20=2.16 - can someone please tell me where all three values came from?

it then says Median is 40+216 = 42.16<--- (final answer, please explain as well)

I'd prefer if it can be explained in the proportionality method as mentioned in the answer book

Also if someone can give me a run down of the area method additionally then I wouldnt mind either