value of x by back-solving. First, start with 3. If x = 3, then traveling at 15 mph,
Bob traveled a distance of 15(3) = 45. Traveling 20 mph for (3 − 1) hours, Bob
traveled 40 miles. 3 is too small for the distances to match. Eliminate A and B.
Now go to Choice D. If x = 5, then traveling at 15 mph, Bob traveled a distance
of 15(5) = 75. Traveling 20 mph for (5 − 1) hours, Bob traveled 80 miles. 5 is
too large for the values to match. Eliminate D and E. The answer is C.- A and B Back-solving is a good strategy here, but make sure to check all the
choices. Try Choice A. If y = 3, then 3x = 12 → x = 4. These values satisfy the
equation: x + y = 7. Thus 3 is a potential answer. Go through this process for all
the choices. The only other choice that provides a value that will yield a value
for x that satisfies both equations is 4. The answer is A and B. - A Back-solve by starting with Choice B. If b = 8, then
a^2 + 8 = 7
a^2 = −1
A number raised to an even exponent never yields a negative result. Thus 8 is
too large for B. The correct answer must be A. - A
Step 1: Choose smart values: Let y = 100, x = 25, and z = 5.
Step 2: Substitute 100 for y, 20 for x, and 5 for z in the question and
determine the “goal”: If there were originally 25 people and 5 people
dropped out, then the bill will be split among 25 – 5 = 20 people. The total
bill is $100, so after the friends drop out, the cost per person will be
100/20 = 5. The goal is 5.
Step 3: Substitute 100 for y, 20 for x, and 5 for z in the choices, and identify
which choice yields a value that matches your goal: 5. The only choice that
yields a value of 5 is A. - B
Step 1: Choose a smart value: Let z = 200.
Step 2: Substitute 200 for z in the question and determine the “goal”:
If the retailer paid $200 for 50 phones, then each phone cost $4. If the
dealer charged 25% more than he paid for it, he sold each phone for
4 + 0.25(4) = 5. The goal is 5.
Step 3: Substitute 200 for z in the choices, and identify which choice yields
a value that matches your goal: 5. The only choice that yields a value of 5
is B. - E
Step 1: Choose a smart value: To ensure that the number of tapes that Bob
has is an integer, choose a multiple of 3 for y: 6.
Step 2: Substitute 6 for y in the question and determine the “goal”: If Sam
has 6 tapes, then Bob has 2 tapes, and Tom has 12 tapes. In total, they have
6 + 2 + 12 = 20 tapes.
158 PART 3 ■ GRE QUANTITATIVE REASONING02-GRE-Test-2018_107-172.indd 158 13/05/17 11:06 am