Cheat sheet

GMAT Quantitative Reasoning Cheat Sheet

Quick Facts

Section
GMAT Quantitative Reasoning
Questions
21 Problem Solving
Time
45 minutes
Pace
About 2:09 per question
Calculator
None in Quant
Section score
60-90
Total score
205-805
Geometry
Not tested
Data Sufficiency
Now in Data Insights
Answer edits
Up to 3 per section
Fee
$275 center, $300 online
Score validity
5 years

Problem Solving vs Data Sufficiency

Problem Solving

  • Quant section only
  • Five answer choices
  • Solve for a value

Data Sufficiency

  • Data Insights section
  • Asks if data suffices
  • Never fully solve

Quant vs Data Insights

Method Picker

  1. Variables in the choicesPlug in numbers(Try 2, 10, 100)
  2. Numbers in the choicesBacksolve(Start at middle)
  3. Choices far apartEstimate(Round and bound)
  4. Choices very closeCompute exactly(No rounding)
  5. Percent word problemAssume 100(Simplest base)
  6. Ratio with no totalIntroduce k(Total is a multiple)
  7. Must be trueTest counterexamples(Try 0, 1, negatives)
  8. Ugly arithmeticFactor first(Cancel before multiplying)
  9. Past three minutesGuess and bookmark(Edit later)

Section Format

Questions
21 Problem Solving items
Time
45 minutes, no break
Pace
About 2:09 each
Choices
Five options, one correct
Adaptive
Difficulty follows your answers
Skipping
Not allowed going forward
Review & Edit
Change up to 3Per section
Calculator
None; scratch pad only
Section order
Choose any order
Unfinished penalty
Score reduced significantly

Plug In vs Solve Algebraically

Plug in numbers

  • Variables in choices
  • Pick simple values
  • Check all choices

Solve algebraically

  • Numbers in choices
  • Cleaner short setups
  • Fewer arithmetic slips

Test vs derive

Scoring + Retakes

Section score
60-90, 1-point steps
Total score
205-805
Weighting
Quant, Verbal, Data equal
Pass mark
None; programs set targets
Score preview
Unofficial score shown immediately
Official report
Typically 3-5 business days
Retake wait
16 calendar days
Yearly cap
5 per rolling year
Lifetime cap
Removed October 2024
Validity
5 years from test
Free reports
5 programs included

Answer Choice Strategy

Read choices first
They reveal needed precision
Spread choices
Estimate, then eliminate
Close choices
Compute exactly
Backsolving
Start at middle choice
Plug in numbers
Pick easy safe values
Avoid 0 and 1
They behave unusually
Trap answers
Match partial-step results
Guess and move
Past three minutes
Bookmark
Flag for later edit

Mental Math Toolkit

Squares 1-15
Memorize through 225
Cubes 1-10
Memorize through 1,000
1/8
12.5%
1/6
About 16.67%
1/7
About 14.29%
3/8
37.5%
Powers of 2
2, 4, 8, 16, 32
Doubling and halving
Simplifies awkward products
Factor before multiplying
Cancel early, compute less
Benchmark 10%
Scale to other percents

Digit Sum Rules

Sum the digits: 3 and 9 both test

3: sum divisible by 39: sum divisible by 9Works at any length

Factor vs Multiple

Factor

  • Divides the number
  • Never exceeds it
  • Finite count

Multiple

  • Number times an integer
  • Never smaller
  • Infinite count

Divides vs divisible

Number Properties Picker

  1. Asks about remaindersDivision algorithm(Remainder below divisor)
  2. Asks about divisibilityDigit-sum rules(3 and 9)
  3. Counts the factorsPrime factorization(Add 1 to exponents)
  4. Units digit of powerCycle of four(Use exponent remainder)
  5. Terminating or repeatingCheck denominator primes(Only 2s and 5s)
  6. Even or odd resultParity rules(Signs do not matter)
  7. Largest common divisorGCF(Lowest shared powers)

Divisibility Rules

2
Last digit is even
3
Digit sum divisible by 3
4
Last two digits divisible
5
Ends in 0 or 5
6
Passes 2 and 3
8
Last three digits divisible
9
Digit sum divisible by 9
10
Ends in 0
11
Alternating digit sum works
12
Passes 3 and 4

Units Digit Cycles

Powers cycle every four; divide the exponent by 4

2: 2, 4, 8, 63: 3, 9, 7, 17: 7, 9, 3, 1Remainder 0 means last

Primes + Factors

Primes under 50
Fifteen of them2 to 47
Only even prime
2
1 is not prime
Needs exactly two divisors
Prime test
Trial-divide to sqrt n
Factor count
Add 1 to exponents
72
2^3 x 3^2 gives 12
GCF
Lowest shared prime powers
LCM
Highest prime powers
GCF x LCM
Equals product of numbers
Perfect square
All exponents are even

Exponents + Roots

a^m x a^n
a^(m+n)
a^m / a^n
a^(m-n)
(a^m)^n
a^(mn)
(ab)^n
a^n x b^n
a^0
1 for nonzero a
a^(-n)
1/a^n
a^(1/2)
sqrt a
sqrt(ab)
sqrt a x sqrt b
sqrt(a^2)
|a|, not always a
Negative base
Even power gives positive
0 < x < 1
Squaring makes it smaller

Number Line + Signs

Even + even
Even
Odd + odd
Even
Even x odd
Even
Odd x odd
Odd
Negative x negative
Positive
Zero
Even, neither positive nor negative
Zero product
Some factor equals zero
Consecutive integers
Product divisible by n!
Remainder range
0 <= r < divisor
Division algorithm
dividend = divisor x quotient + remainder
Absolute value
Distance from zero

Decimals + Place Value

Terminating decimal
Denominator only 2s, 5s
Repeating decimal
Denominator has other primes
Rounding
Look one digit right
Scientific notation
One digit before point
Multiply by 10^n
Shift point right
Place value
Tenths, hundredths, thousandths
Percent to decimal
Divide by 100

Order of Operations

PEMDAS: parentheses, exponents, multiply, divide, add, subtract

Work left to rightMultiply and divide tieAdd and subtract tie

Algebra Move Picker

  1. Equation equals zeroFactor it(Zero product property)
  2. Two equations, two unknownsSubstitute or eliminate(Check for parallel)
  3. Squared binomial appearsUse the identity((a+b)^2)
  4. One square minus anotherDifference of squares(Fast factoring)
  5. Inequality times negativeFlip the sign(Adding never flips)
  6. Absolute value equationSplit into cases(Check both roots)
  7. Asks for root sumUse -b/a(Skip the formula)

Factoring Patterns

Difference of squares
a^2 - b^2 = (a+b)(a-b)
Perfect square
(a+b)^2 = a^2+2ab+b^2
Negative square
(a-b)^2 = a^2-2ab+b^2
Common factor
Pull out shared term
Trinomial
Find two factors of c
79 x 81
80^2 - 1 = 6,399
FOIL
First, outer, inner, last
Zero product
Set each factor zero

Quadratics

Standard form
ax^2 + bx + c = 0
Quadratic formula
-b +/- sqrt D over 2a
Discriminant
b^2 - 4ac decides roots
D > 0
Two real roots
D = 0
One repeated root
D < 0
No real roots
Root sum
-b/a
Root product
c/a

Inequalities + Absolute Value

Negative multiply
Flip the sign
Adding
Never flips the sign
Unknown divisor
Never divide by variable
|x| < a
-a < x < a
|x| > a
Two separate intervals
|x-3| < 2
1 < x < 5
Squaring an inequality
Safe only when positive
Reciprocal
Positive terms reverse order
Compound inequality
Operate on all parts

Functions + Sequences

f(x)
A rule, not multiplication
f(g(x))
Inner function first
Domain
Allowed input values
Undefined
Zero denominator, negative root
Arithmetic term
a_1 + (n-1)d
Arithmetic sum
n(a_1 + a_n)/2
Geometric term
a_1 x r^(n-1)
Evenly spaced mean
(first + last)/2
Off-by-one
Mind the n-1

Coordinate Plane

Slope
(y2-y1)/(x2-x1)
Slope-intercept
y = mx + b
y-intercept
Set x = 0
x-intercept
Set y = 0
Parallel lines
Same slope, different intercept
Perpendicular
Slopes multiply to -1
Distance
sqrt of squared differences
Midpoint
Average both coordinates
Quadrant I
Both coordinates positive

Translation Keywords

is
equals
of
multiply
per
divide
sum, more than
add
difference, less than
subtract
5 less than y
y - 5
twice
multiply by 2
consecutive
n, n+1, n+2
what percent
x/100 times

Rate Time Distance

D = R x T; cover one, read the rest

R = D/TT = D/RRates add, times do not

Simple vs Compound Interest

Simple

  • P x r x t
  • Interest on principal
  • Linear growth

Compound

  • P(1 + r/n)^(nt)
  • Interest on interest
  • Exponential growth

Principal vs balance

Word Problem Picker

  1. Two objects movingRelative speed(Add or subtract)
  2. Two workers togetherAdd the rates(1/T = 1/a + 1/b)
  3. Round trip speedsTotal distance over time(Never average speeds)
  4. Solutions being mixedTrack the solute(volume x concentration)
  5. Price then discountMultiply the factors(Order does not matter)
  6. Interest over yearsCompound formula(P(1+r)^t)
  7. Cost versus selling priceCheck markup or margin(Different denominators)
  8. Units do not matchConvert first(Cancel the units)

Percent Formulas

Percent change
(new - old)/old x 100
Base of percent
Always the original value
Increase 25%
Multiply by 1.25
Decrease 20%
Multiply by 0.80
Successive changes
Multiply factors, never add
+15% then -20%
Net 8% decrease
Percent to fraction
Divide by 100
Reverse a percent
Divide, do not subtract

Percent Change Base

Change over original; the original is always the base

40 to 50 is 25%50 to 40 is 20%Denominator never switches

Percent Of vs More Than

20% of y

  • x = 0.2y
  • A fraction of y
  • Smaller than y

20% more than y

  • x = 1.2y
  • Added on top
  • Larger than y

Multiply vs add

Ratios + Proportion

Ratio a : b
Quantities ak and bk
Total parts
(a + b)k
Ratios hide totals
Need one actual value
a/b = c/d
Cross multiply: ad = bc
Direct variation
y = kx
Inverse variation
xy = k
Scaling a recipe
Multiply every part equally
Three-term ratio
Match shared term first

Markup vs Margin

Markup

  • Profit over cost
  • Cost is denominator
  • $20/$80 = 25%

Margin

  • Profit over price
  • Price is denominator
  • $20/$100 = 20%

Cost vs selling price

Rate, Work, Distance

Distance
rate x time
Time
distance / rate
Average speed
total distance / total time
Never average speeds
Weight by time spent
Combined work
1/T = 1/a + 1/b
Two workers
T = ab/(a+b)
Rates add
Times never add
Opposite directions
Add the speeds
Same direction
Subtract the speeds
Downstream
boat + current
Upstream
boat - current

Mixtures + Interest

Solute amount
volume x concentration
Mixing
Solute amounts add
Weighted average
Falls between component values
Simple interest
P x r x t
Compound interest
P(1 + r/n)^(nt)
Annual compounding
P x (1+r)^t
Doubling estimate
Rule of 72
Profit
revenue - cost

Unit Conversion

Conversion fraction
Equals 1, cancels units
km/h to m/s
Multiply by 5/18
m/s to km/h
Multiply by 18/5
Check units
Units must cancel cleanly
Mixed units
Convert before computing
Rate units
Numerator over denominator

Order Test

Order matters? Permute. Order ignored? Combine.

Ranking: permutationCommittee: combinationHandshake: combination

Permutation vs Combination

Permutation

  • Order matters
  • n!/(n-r)!
  • Rankings, passwords

Combination

  • Order ignored
  • n!/(r!(n-r)!)
  • Committees, handshakes

Arrange vs choose

Counting Picker

  1. Order changes the outcomePermutation(n!/(n-r)!)
  2. Order is irrelevantCombination(n!/(r!(n-r)!))
  3. Independent stagesMultiply outcomes(Counting principle)
  4. Repeated identical itemsDivide by factorials(Remove duplicates)
  5. Asks at least oneComplement(1 - P(none))
  6. Two overlapping groupsVenn formula(Subtract the overlap)
  7. Seats in a circleFix one seat((n-1)! arrangements)

Average + Spread

Mean
Sum divided by count
Sum
mean x count
Median
Middle of ordered list
Even count median
Average two middle values
Mode
Most frequent value
Range
Largest minus smallest
Standard deviation
Spread about the mean
Add a constant
Deviation unchanged
Multiply by k
Deviation scales by k
Identical values
Standard deviation is 0
Symmetric set
Mean equals median

Mean vs Median

Mean

  • Sum over count
  • Outliers pull it
  • Recovers the total

Median

  • Middle ordered value
  • Outlier resistant
  • Better for skew

Average vs middle

Sets + Venn

Two-set total
A + B - Both + Neither
Union
|A| + |B| - overlap
Double counted
Subtract the overlap once
Neither
Outside both circles
Maximum overlap
Size of smaller set
Minimum overlap
A + B - Total
Three sets
Add back triple overlap

Range vs Standard Deviation

Range

  • Largest minus smallest
  • Only two values
  • Ignores the middle

Standard deviation

  • Spread about mean
  • Uses every value
  • Shifting changes nothing

Endpoints vs spread

Counting Methods

Counting principle
Multiply stage outcomes
Arrangements
n! orderings
0!
Equals 1
Permutation
n!/(n-r)!
Combination
n!/(r!(n-r)!)
Order matters
Use a permutation
Order ignored
Use a combination
Identical items
Divide by repeat factorials
Circular seating
(n-1)! arrangements
Handshakes
C(n, 2)

Probability Rules

Basic probability
favorable / total outcomes
Range
Between 0 and 1
Complement
1 - P(E)
At least one
Use 1 minus none
Or rule
P(A) + P(B) - both
Mutually exclusive
Overlap term is zero
And, independent
P(A) x P(B)
Dependent events
Adjust after first draw
Without replacement
Denominator shrinks each draw

Series + Estimation

Consecutive sum
n(first + last)/2
First n integers
n(n+1)/2
Evenly spaced count
(last - first)/step + 1
Geometric ratio
Each term times r
Choices spread out
Round and bound
Choices close together
Exact arithmetic needed
Rounding both up
Overstates the product
Keep one exact
Bound the error direction

Common Traps

Average speed

Weight by time Not average of speeds

Successive percents

Multiply the factors Never add the percents

Squares and roots

sqrt(x^2) is |x| Not always x

Zero and one

Zero is even One is not prime

Inequality sign

Negative multiply flips Adding never flips

Ratio is not a total

3 : 5 means 3k, 5k Actual amounts need k

Rates versus times

Rates add directly Times never add

Median is not mean

Median ignores outliers Mean follows them

No calculator

Quant forbids calculators Data Insights allows one

Geometry removed

No triangles or circles Coordinate lines still tested

Last Minute

  1. 1.21 questions, 45 minutes, no calculator
  2. 2.Pace about 2:09 per question
  3. 3.Only Problem Solving; no Data Sufficiency
  4. 4.Geometry gone; coordinate lines stay
  5. 5.Section scored 60-90; total 205-805
  6. 6.Edit up to 3 answers
  7. 7.Percent change uses the original
  8. 8.Average speed uses total time
  9. 9.Rates add; times do not
  10. 10.Order matters means permutation
  11. 11.Negative multiply flips the inequality
  12. 12.Factor count: add 1 to exponents
  13. 13.At least one = 1 minus none
  14. 14.Sum = mean x count
  15. 15.sqrt of a square is absolute
  16. 16.Never leave a question blank
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