PracticeQuantitative · Data Insights
GMAT percentage practice questions
These questions focus on the decisions percentages conceal: the correct base, the requested quantity, and whether the base changes between steps. The calculations are secondary.
That is not a stylistic choice. In a percentage question that a strong candidate misses, the arithmetic is almost never what went wrong. What went wrong is a decision made two lines earlier about which number the change is being measured against.
What this set trains
- Choosing the reference base when two plausible candidates are in the stem
- Reverse percentages — recovering an original from a post-change figure without dividing by the wrong side
- Successive changes that do not add, because the second one acts on a base the first one moved
- Percentage points versus percent — a rise from 4% to 6% is two points and fifty percent, and the answer choices will contain both
- Counts versus rates, where the larger percentage belongs to the smaller group
Two traps account for most of the misses here: Denominator or Base-Rate Confusion and Requirement Misread. The explanations name which one a given wrong answer suggests.
A parking garage charges $2.50 upon entry plus $0.75 for each 20 minutes or fraction thereof parked. For every number x, [x] is defined to be the least integer greater than or equal to x. Which of the following represents the charge, in dollars, for parking t hours?
Answer: C
Since 20 minutes is 1/3 hour, a parking time of t hours contains t ÷ (1/3) = 3t twenty-minute intervals. The rounded number of intervals is [3t], so the charge is 2.50 + 0.75[3t], making C correct. Choice A divides by 3 instead of by 1/3. Choice B rounds 0.25t, placing the rate inside the ceiling with the wrong divisor. Choice D rounds 2.25t, which multiplies 0.75 by 3 but then omits the outside 0.75 multiplier. Choice E charges only for whole hours.
Original GMAT-style question written for Premiergrad and checked by an independent blind solve. Not an official GMAT question.
A restaurant recorded the tip rate (tip amount divided by pre-tax bill, as a decimal) for two meals: Meal 1 had a tip rate of t1/b1, and Meal 2 had a tip rate of t2/b2, where all amounts are positive. If Meal 1's tip rate was lower than Meal 2's, which of the following must be between the two tip rates? I. (t1 + t2)/(b1 + b2) II. (t1*t2)/(b1*b2) III. t2/b2 - t1/b1
Answer: B
The combined tip rate (t1 + t2)/(b1 + b2) is the mediant of the two positive decimals. Since t1/b1 < t2/b2, we have t1*b2 < t2*b1. Cross-multiplication shows t1/b1 < (t1 + t2)/(b1 + b2) and (t1 + t2)/(b1 + b2) < t2/b2, so I must be between the two tip rates. The product (t1*t2)/(b1*b2) need not be between; for t1/b1 = 1/4 and t2/b2 = 1/2, the product is 1/8, below both rates. The difference t2/b2 - t1/b1 need not be between; for t1/b1 = 2/5 and t2/b2 = 3/5, the difference is 1/5, below the lower rate 2/5. Therefore only I must be between.
Original GMAT-style question written for Premiergrad and checked by an independent blind solve. Not an official GMAT question.
A dealer purchased 60 vintage guitars at $16 7/8 per guitar and sold them all at $41 per guitar. The dealer paid a 2.5 percent auction fee on the total purchase price and a 7 percent commission on the total selling price. Which of the following is closest to the dealer's percent gain on this investment?
Answer: B
Total purchase price: 60 x $16.875 = $1,012.50. Purchase fee: 2.5% of $1,012.50 = $25.3125, so total investment cost = $1,037.8125. Total sale price: 60 x $41 = $2,460. Sale fee: 7% of $2,460 = $172.20, so net proceeds = $2,287.80. Gain = $2,287.80 - $1,037.8125 = $1,249.9875. Percent gain = $1,249.9875 / $1,037.8125 x 100 = about 120.4%, closest to 120%. The 126% option uses the sale fee but omits the purchase fee; 137% uses the purchase fee but omits the sale fee; 143% omits both fees; 55% divides the gain by net proceeds.
Original GMAT-style question written for Premiergrad and checked by an independent blind solve. Not an official GMAT question.
Let S be the sum of the reciprocals of the consecutive integers from 751 to 760, inclusive. Which of the following is less than S?
I. 0.014 II. 0.013 III. 1/70
Answer: C
There are 10 terms. Each term is at least 1/760, so S > 10/760 = 1/76 ≈ 0.0131579. Thus 0.013 is less than S. Each term is at most 1/751, so S < 10/751. Since 10/751 < 0.014 (cross-multiply: 10 × 500 = 5000 < 7 × 751 = 5257), both 0.014 and 1/70 are greater than S. Therefore only II is less than S.
Original GMAT-style question written for Premiergrad and checked by an independent blind solve. Not an official GMAT question.
At a marathon expo, 35% of all attendees picked up a race packet. Of those who picked up a race packet, 2/5 also purchased merchandise. If 1,400 attendees both picked up a race packet and purchased merchandise, how many attendees were at the expo?
Answer: A
The number of attendees who picked up a race packet is 1,400 ÷ (2/5) = 3,500. Since packet pick-up attendees are 35% of all expo attendees, the total is 3,500 ÷ 0.35 = 10,000. Choice B stops at the packet-pickup subtotal. Choice C divides 1,400 by 0.35, ignoring the 2/5 fraction. Choice D multiplies by 2/5 instead of dividing. Choice E reflects a decimal-place error in handling 35%.
Original GMAT-style question written for Premiergrad and checked by an independent blind solve. Not an official GMAT question.
Your result on the public set
— / 5
5 of 17 questions in this collection are public.
- A raw score out of 5 tells you very little on its own — the useful signal is the shape of the misses, and that is what the notes under each question describe.
- If two or more of your wrong answers were correct work on a different target, that is a pattern rather than a bad day.
Reading your own result
Look at the shape of the misses rather than the count.
- Wrong answers that are correct arithmetic on a different target — you are losing the requirement between reading and solving. The fix is a written target label, not more percentage practice.
- Wrong answers that are off by exactly the base — 12/92 where 12/80 was asked. The concept is intact; the reference selection is not.
- Wrong answers scattered with no pattern — more likely a genuine concept gap. Percentages covers how the exam frames the idea.
The distinction matters because the three cases need three different weeks of work, and the raw score of 2/5 is identical in all three.
What Lumen looks for
Lumen reads the answer you chose, not just whether it was wrong. On a question like this it separates three things that all look identical in a score: a concept you have not met, a reasoning step that went sideways, and a correct method pointed at the wrong target. Those need three different next weeks, and only the third one is fixed by re-reading the topic.
A single answer is weak evidence and Lumen says so. It becomes a diagnosis when the same shape shows up across several questions — which is the part a page like this cannot do for you.
Related
-
Concept
Percentages
The GMAT rarely tests whether you remember:
What the exam is testing when it asks for a percentage.
-
Trap
Denominator or Base-Rate Confusion
Denominator or Base Rate Confusion occurs when a rate, percentage, or relative change is interpreted without preserving…
The trap behind most misses in this set.
-
Concept
Graphics Interpretation
GMAT Graphics Interpretation questions test whether you can decode what a visual represents before you calculate or…
The same decision, read off a chart.
Continue the full set
The questions above are the public part of this collection. An account adds the rest of the set, your attempts saved, and a diagnosis of the answer you actually chose rather than a general explanation.
Continue with the full set Everything on this page stays free and open — no account needed to read it or to attempt the questions above.