🏆 Top 50 Mistakes
The 50 most common misconceptions in GCSE Mathematics
Thinking $(a + b)^2 = a^2 + b^2$
"The Binomial Blunder"
Algebra & GraphsAdding the percentage instead of multiplying
"The Add-On Error"
Number & ProportionDividing by one ratio part instead of the total
"The Part-Total Mixup"
Number & ProportionForgetting to change the sign when moving terms
"The Sign Slip"
Algebra & GraphsDividing by the new value instead of the original
"The Denominator Disaster"
Number & ProportionErrors when expanding negative brackets
"The Negative Neglect"
Algebra & GraphsFinding percentage of final amount for reverse problems
"The Backwards Blunder"
Number & ProportionMoving the decimal point the wrong way
"The Backwards Shift"
Number & ProportionFinding $c^2$ instead of $c$
"The Forgotten Root"
Geometry & ShapesAdding when finding a shorter side
"The Plus-Minus Mixup"
Geometry & ShapesOnly doing the operation on one side
"The One-Sided Operation"
Algebra & GraphsGetting the ratio the wrong way round
"The Flip"
Number & ProportionConfusing opposite and adjacent sides
"The O-A Swap"
Geometry & ShapesErrors when collecting x terms
"The Collection Confusion"
Algebra & GraphsDividing numerator and denominator by different numbers
"The Unequal Split"
Number & ProportionUsing 180° as the sum for all polygons
"The Triangle Default"
Geometry & ShapesLabelling the wrong side as the hypotenuse
"The Hypotenuse Hijack"
Geometry & ShapesNot applying operations to entire expressions
"The Partial Operation"
Algebra & GraphsNot taking out the highest common factor
"The Partial Factor"
Algebra & GraphsCalculator set to radians instead of degrees
"The Mode Mishap"
Geometry & ShapesNot using inverse functions to find angles
"The Inverse Forget"
Geometry & ShapesDividing the wrong way round
"The Fraction Flip"
Algebra & GraphsConfusing interior and exterior angle formulas
"The Inside-Out Error"
Geometry & ShapesUsing diameter instead of radius in circle formulas
"The D-R Disaster"
Geometry & ShapesForgetting to square root or doing it incorrectly H
"The Root of the Problem"
Algebra & GraphsUsing slant height instead of perpendicular height
"The Slant Slip"
Geometry & ShapesThinking percentage means out of 100 literally
"The Literal Hundred"
Number & ProportionGiving shares to the wrong people
"The Swap Error"
Number & ProportionMixing up alternate and co-interior angles
"The Z and C Confusion"
Geometry & ShapesForgetting the ½ in triangle area
"The Missing Half"
Geometry & ShapesAdding highest and lowest instead of subtracting
"The Range Reversal"
Probability & StatisticsGiving the position as the answer instead of the value
"The Position Problem"
Probability & StatisticsSubtracting the wrong value for complementary events
"The Complement Confusion"
Probability & StatisticsMixing up percentage and decimal forms
"The Percentage Pickle"
Probability & StatisticsConfusing expected frequency with probability
"The Expected Error"
Probability & StatisticsAssuming outcomes are equally likely when they are not
"The Fair Fallacy"
Probability & StatisticsNot adjusting after calculation
"The Unadjusted Answer"
Number & ProportionConfusing gradient and y-intercept
"The m-c Mixup"
Algebra & GraphsFinding median without ordering data first
"The Middle Muddle"
Probability & StatisticsAveraging the values column instead of using frequencies
"The Frequency Forgetter"
Probability & StatisticsUsing class boundaries instead of midpoints
"The Boundary Blunder"
Probability & StatisticsGiving probability greater than 1
"The Impossible Probability"
Probability & StatisticsUsing wrong total for denominator
"The Total Trouble"
Probability & StatisticsUsing simple interest formula for compound interest
"The Simple Mistake"
Number & ProportionOnly giving one solution to a quadratic
"The Missing Root"
Algebra & GraphsUsing 1 + r instead of 1 - r for depreciation
"The Depreciation Direction"
Number & ProportionSolving without setting equal to zero first
"The Zero Forgetter"
Algebra & GraphsForgetting to include radii in sector perimeter
"The Missing Radii"
Geometry & ShapesSign errors in the quadratic formula H
"The Formula Fumble"
Algebra & GraphsGetting the angle fraction upside down
"The Fraction Flip"
Geometry & ShapesDividing by x and losing a solution
"The Vanishing Root"
Algebra & GraphsCancelling terms instead of factors
"The Term Terminator"
Algebra & GraphsHaving A greater than or equal to 10
"The Ten Trap"
Number & ProportionNot multiplying all terms when finding common denominator
"The Missing Multiply"
Algebra & GraphsUsing wrong sign for small numbers
"The Sign Slip"
Number & ProportionJoining plotted points with straight lines
"The Connect-the-Dots"
Algebra & GraphsCalculating gradient with x over y instead of y over x
"The Gradient Flip"
Algebra & GraphsUsing the wrong inequality sign for upper bound H
"The Inequality Slip"
Number & Proportion