Rental firm has only two types of vehicles: Minivans and Sedans
Runs on exactly two types: Gasoline or Electricity
We need to know if P(sedan running on electricity ) > P(minivan running on gasoline)
Lets define the required 4 possible combinations:
Minivan + Gasoline - P(MG)
Minivan + Electric - P(ME)
Sedan + Gasoline - P(SG)
Sedan + Electric - P(SE)
=> P(SE) > P(MG) ?
We know that P(MG) + P(ME) + P(SG) + P(SE) = 1 (Entire count of vehicles possible)
Given 2 statements:
(1) The probability that a randomly selected vehicle is either a minivan or runs on gasoline is 2/5.
P(M or G) = P(MG) + P(ME) + [P(MG) + P(SG)] - P(MG) {Eliminate one instance of P(MG) since double count)}
2/5 = P(MG) + P(ME) + P(SG)
Cant answer P(SE) > P(MG) ?
Statement 1 is insufficient
(2) The probability that a randomly selected vehicle is either a sedan or runs on electricity is 5/8.
P(S or E) = P(SG) + P(SE) + [P(ME) + P(SE)] - P(SE) {Eliminate one instance of P(SE) since double count)}
5/8= P(SG) + P(SE) + P(ME)
Cant answer P(SE) > P(MG) ?
Statement 2 is insufficient
Lets combine statement (1) and (2)
2/5 = P(MG) + P(ME) + P(SG) -------- A
5/8= P(SG) + P(SE) + P(ME) ------ B
Now, we subtract equation A from B,
=> P(SG) + P(SE) + P(ME) -[ P(MG) + P(ME) + P(SG) ] = 5/8 - 2/5
=> P(SG) + P(SE) + P(ME) - P(MG) - P(ME) - P(SG) = 9/40
=> P(SE) - P(MG) = 9/40
This is only possible if P(SE) > P(MG)
So,
C. Both statements together are sufficient, but neither alone is sufficient.