Please help on these PS questions!

Hi srinivasapriyan.r,

While you should only post 1 question at a time, here are the solutions to the questions (I'll do 1 per post):

Question 1:

4 regular apples, 1 spoiled apple. If you grab 2 apples, what's the probability of getting the spoiled apple?

The question can be solved in a couple of ways. Here's one way to do it:

1st regular, 2nd spoiled = (4/5)(1/4) = 4/20
1st spoiled, 2nd regular = (1/5)(4/4) = 4/20

Total ways to get 1 spoiled and 1 regular = 4/20 + 4/20 = 8/20 = 2/5

Final Answer: C

GMAT assassins aren't born, they're made,
Rich

Hi srinivasapriyan.r,

Question 2:

For which of the following questions is the f(x) = f(1-x)?

This type of question is perfect for TESTing Values.

If X = 0, then we need a function that has the same result for f(0) and for f(1-0)

So, plug 0 and 1 into each of the 5 options and find the answer that has the same result for both.

A: f(0) = 1, f(1) = 0 NOT a match
B: f(0) = 1, f(1) = 0 NOT a match
C: f(0) = -1, f(1) = 1 NOT a match
D: f(0) = 0, f(1) = 0 THIS MATCHES
E: f(0) = 0, f(1) = undefined NOT a match

Final Answer: D

GMAT assassins aren't born, they're made,
Rich

Hi srinivasapriyan.r,

Question 3:

6 machines, working at the same constant rate, can finish a job in 12 days. How many EXTRA machines will you need to finish the job in 8 days?

This type of question is easiest to solve if you convert the info into "work units"

Here, we start with 6 machines working for 12 days. This equals 6x12 = 72 machine-days of work to finish the job.

If we wanted to finish the job in 8 days, it would still take 72 machine-days of work, so we'd need 72/8 = 9 machines.

We already have 6 machines, so we need 3 MORE machines to get the job done in 8 days.

Final Answer: B

GMAT assassins aren't born, they're made,
Rich