McGraw-Hill Education GRE 2019

If a coin is flipped three times, the probability that it

will land on heads all three times is 0.064.

QUANTITY A QUANTITY B

4. A B C D

Exercise Answers

Discrete Quantitative Questions

1. E Use the fundamental counting principle: 4 × 5 × 3 = 60.


2. 14 First, calculate how many multiples of 4 there are from 1–100, inclusive.
   Recall that the formula to calculate the number of items in an evenly spaced
   set is:
   last – first
   spacing + 1
   Thus the number of multiples of 4 from 1–100, inclusive, is 100 – 4 4 + 1 = 25.
   There are thus 25 desired outcomes. Since there are 100 total outcomes, the
   probability of selecting a multiple of 4 is 10025 =^14.


3. C Since the question concerns the probability that multiple events will occur,
   multiply the probabilities of each desired event. The probability of rain on
   Monday is 0.6. The probability that it won’t rain on Tuesday is 1 – 0.6 = 0.4.
   Thus the probability that it will rain on Monday, but not on Tuesday, is 0.4 ×
   0.6 = 0.24.


4. A Since the question concerns the probability that multiple events will occur,
   multiply the probabilities of each event. Since there are three prime numbers
   from 1–6 (2, 3, and 5), the probability that the die will land on a prime number
   on a single roll is^36 = 0.5. The probability that the die will land on a prime
   number on all three rolls is thus 0.5 × 0.5 × 0.5 = 0.125.


5. C Since the question concerns the probability that multiple events will occur,
   multiply the probabilities of each event. The probability that the first employee
   selected is not a doctor is^6080 =^34. After the first employee is chosen, there are
   79 total employees and 59 total nondoctors left. Thus the probability that the
   second employee selected will also be a doctor is^5979. Since the question says
   “closest to,” you can estimate^5979 as roughly^6080 =^34. The approximate probability
   that neither employee is a doctor is thus^34 ×^34 = 0.75 × 0.75 = 0.5625. The
   closest answer is C.


6. A Since multiple events must be satisfied to yield a desired outcome, you
   should multiply the individual probabilities of each desired event. The
   probability that the first marble chosen is red is 217 =^13. The probability that the
   second marble chosen is red is also 217 =^13.^13 ×^13 =^19.


7. C The word arrangement indicates that this is a permutation question and
   that you should thus use the slot method. You should set up three slots. There
   are five possibilities for the first slot, four possibilities for the second slot, and
   three possibilities for the third slot:

The probability that the

coin will land on tails

on any given flip

0.5

362 PART 4 ■ MATH REVIEW

04-GRE-Test-2018_313-462.indd 362 12/05/17 12:04 pm