Cheat sheet

ACT Math Cheat Sheet

Number + Quantity

10-12%of exam

Number RulesExponentsRadicalsComplex NumbersSequences

Algebra

17-20%of exam

Functions

17-20%of exam

FunctionsDomainCompositionTransformsLogs

Geometry + Trig

17-20%of exam

Stats + Probability

12-15%of exam

Data + StatsProbability + CountingRegressionOutliersPermutations

Essential Skills

20%of exam

RatesPercentsProportionsUnitsStrategy Picker

Quick Facts

Section
Math
Questions
45
Scored
41
Time
50 min
Pace
67 sec/item
Score
1-36
Calculator
Permitted
Core split
80% + 20%

Number Rules

a^m*a^n
Add exponents
a^m/a^n
Subtract exponents
a^-n
Move across fraction
a^(m/n)
Root then power
i^2
-1
Absolute value
Distance from zero

Sequences + Matrices

Arithmetic
Add constant
Geometric
Multiply ratio
Matrix product
Inner dimensions match
Result size
Outer dimensions
Vector
Magnitude + direction
Set
Collection of values

FOIL

First, Outer, Inner, Last

Binomial productsCombine like termsCheck signs

Slope vs Intercept

Slope

  • Rate of change
  • m
  • Rise/run

Intercept

  • Axis crossing
  • b or zero
  • Starting value

Rate vs start

Formula Picker

  1. Line rateSlope(rise/run)
  2. Two points apartDistance(coordinate theorem)
  3. Quadratic rootsFactor/formula(fastest route)
  4. Circle centerStandard form(signs flip)
  5. Right trianglePythagorean/trig(angle decides)
  6. Percent growthExponential(1+r factor)

Algebra Moves

Linear equation
Isolate variable
Inequality
Flip on negative
System
Substitute or eliminate
Factoring
Product and sum
Quadratic formula
Use when unfactorable
Radical equation
Check extra roots

Graphs + Lines

Slope
Rise over run
y=mx+b
Slope-intercept form
Point-slope
Use point + slope
Distance
Pythagorean on coordinates
Midpoint
Average coordinates
Perpendicular
Negative reciprocal slopes

Domain vs Range

Domain

  • Allowed inputs
  • x-values
  • Check restrictions

Range

  • Possible outputs
  • y-values
  • Check graph

Input vs output

Functions

f(a)
Substitute input
Domain
Allowed inputs
Range
Possible outputs
f(g(x))
Do g first
Inverse
Swap x and y
Piecewise
Choose interval first

Function Models

Vertical shift
f(x)+k
Horizontal shift
f(x-h)
Exponential
Repeated percent change
Logarithm
Exponent question
Vertex form
Shows turning point
Zero
x-intercept

SOH-CAH-TOA

Sine opposite, cosine adjacent, tangent opposite

SOH: sin O/HCAH: cos A/HTOA: tan O/A

Similar vs Congruent

Similar

  • Same shape
  • Scaled lengths
  • Angles equal

Congruent

  • Same size
  • Same shape
  • Sides equal

Scaled vs identical

Geometry Basics

Triangle sum
180 degrees
Pythagorean
a^2+b^2=c^2
Similarity
Same shape scale
Congruence
Same size shape
Area triangle
1/2 bh
Scale area
k^2 factor

Special Triangles

45s match; 30s double

45: x,x,xsqrt230: x,xsqrt3,2xHypotenuse longest

Circumference vs Area

Circumference

  • Boundary length
  • Linear units
  • 2*pi*r

Area

  • Inside region
  • Square units
  • pi*r^2

Around vs inside

Circles + Solids

Circumference
2*pi*r
Circle area
pi*r^2
Circle equation
Center and radius
Arc length
Angle fraction circumference
Cylinder volume
Base area times height
Scale volume
k^3 factor

Trig

Sine
Opposite over hypotenuse
Cosine
Adjacent over hypotenuse
Tangent
Opposite over adjacent
Radians
pi rad = 180
Unit circle
(cos, sin)
sin^2+cos^2
Equals 1

Probability

Either add; both multiply

Or: add casesAnd: multiply chancesComplement: 1-event

Mean vs Median

Mean

  • Uses all values
  • Outlier sensitive
  • Sum/count

Median

  • Middle value
  • Outlier resistant
  • Sort first

Average vs middle

Data Picker

  1. Average askedMean(sum/count)
  2. Outlier presentMedian(resistant center)
  3. Spread askedStd dev(distance from mean)
  4. Trend askedRegression(line fit)
  5. At least oneComplement(1-none)
  6. Arrangements askedPermutation(order matters)

Data + Stats

Mean
Average
Median
Middle after sorting
Mode
Most frequent
Range
Max minus min
Std dev
Spread from mean
Regression
Best-fit line

Permutation vs Combination

Permutation

  • Order matters
  • Arrangements
  • Lineups

Combination

  • Order ignored
  • Groups
  • Committees

Ordered vs unordered

Probability + Counting

Probability
Favorable over total
Complement
1 minus event
Independent
Multiply probabilities
Conditional
Restrict sample space
Permutation
Order matters
Combination
Order ignored

Independent vs Dependent

Independent

  • No influence
  • Multiply directly
  • Replacement often

Dependent

  • Probability changes
  • Update denominator
  • No replacement

Same odds vs changed

Strategy Picker

  1. Variables messyPlug numbers(simple values)
  2. Choices numericBacksolve(middle first)
  3. Graph shownRead axes(units matter)
  4. Long arithmeticCalculator(avoid keystrokes)
  5. Geometry drawnEstimate(scale clues)
  6. Stuck lateEliminate(keep pace)

Essential Skills

Percent change
Change over original
Unit rate
Per one unit
Proportion
Equal ratios
Weighted avg
Weights before divide
Units
Track every step
Modeling
Translate situation

Common Traps

Negative exponents

Move factor Do not negate

Inequality signs

Negative multiply flips Positive multiply stays

Radius vs diameter

Area needs radius Diameter doubles radius

Squaring roots

Can add solutions Check original equation

Scale factors

Area uses k^2 Volume uses k^3

Order matters

Permutation counts order Combination ignores order

Calculator reliance

Setup comes first Units still matter

Last Minute

  1. 1.Check domain restrictions
  2. 2.Sort before median
  3. 3.Label every unit
  4. 4.Backsolve numeric choices
  5. 5.Slope = rise/run
  6. 6.Area uses square units
  7. 7.Volume uses cubic units
  8. 8.Use radius for circles
  9. 9.Check radical solutions
  10. 10.Estimate geometry drawings
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