Let number of pilots flying Airbus = a
Let number of pilots flying Boeing = b
Let number of pilots flying both Airbus and Boeing = c
a, b and c are non negative integers.
A total of 25 of the pilots fly Boeing airplanes
i.e. a + c = 25, let's call this equation 1
A total of 75 of the pilots fly Airbus airplanes
i.e. b + c = 75, let's call this equation 2
Adding equation 1 and 2 we get: a + b + 2c = 100, let's call this equation 3.
Column 1: largest number of pilots in the group who fly either Boeing or Airbus airplanesi.e. we need to maximize a + b
From equation 3: a + b = 100 - 2c
To maximize a + c we need to minimize b
The maximum value a + b can take is 100.
As 100 is not one of the options we need another constraint for the answer.
Looking at the value of a + b we see that a + b = Even - Even = Even. (because 2c is even)
That means we are left with 2 options a + b = 10 or a + b = 90
a + b cannot be 10 because that would violate equation 1 where c needs to take a value between 65 and 75 as per equation 2, which will not satisfy equation 1.
Hence a + c = 90 from the given option choices.Column 2: the largest number of pilots in the group who possibly could be flying both Boeing and Airbus airplanes.We need to maximize c
From equation 3 we can get the following: c = 50 - (( a+ b) / 2)
Hence the maximum value c can take is 50.
This eliminates 2 option choices (90 and 110)
And the next biggest value c can take is 29.
Hence c = 29 from the given option choices.