Let total number of people in Meg's immediate family = T
Question is: Find T.
Option (1): Everyone in Meg’s immediate family will pay $1,500.
Since total expenditure is $18,000 and each member will pay $1,500, we can calculate 'T' using (18,000/1500) = 12
SUFFICIENT.
Option (2): If 4 immediate family members do not contribute their share, each of the other family members will have to contribute $750 more than if everyone had contributed.
Contribution of each individual can be calculated as, (Total Expenditure/Total People)
If 4 fewer people (i.e T - 4) contribute to the total expenditure, that means per person contribution will increase, i.e. Option (2) can be mathematically written as,
(18000/(T-4)) - (18000/T) = $750
Solving the above equation, we get (T^2 - 4T - 96 = 0)
Solving the quadratic, we get two values of T, i.e. T = 12, T =
-8
Since, the number of people cannot be negative, we get T = 12.
SUFFICIENT.
Since, individually (1) and (2) are sufficient to solve the problem, the answer is Option (D).