So regarding the question I answered it as D

Here’s my reasoning:

S is sum of all fractions and t is less than 50.

So I took,

t=1, S1 = 1 - 1/2 = 1/2

t=2, S2 = 1 - 1/2 + 1 - 1/3 = 2 -(1/2 + 1/3) = 7/6

at t=1 or 2 S < 42

Make a pattern

t=49, S3 = 49 - ( 1/2 + 1/3 + 1/4 + 1/5 … + 1/50) > 42

Used similar logic as Greg did and thought it would be bigger than 42.

So why did Greg consider only 1 case ie for 49?

Shouldn’t multiple cases for t be used?