TSI Assessment Math – Key Rules, Formulas & Quick Reference Guide
(Updated 2025/2026)
(parenthesis, exponents, multiplication, division, addition, subtraction) work left to right -
correct answerPEMDAS
Ex: 6^4, 2^3, 9^10, etc. - correct answerExponential Notation
Ex: 7x7x7, 6x6, 2x2x2x2x2, etc. - correct answerExpanded Form
Ex: 5^2= 25; 25 is the standard notation (the answer or solution) - correct
answerStandard Notation
=+ - correct answer+x+
=- - correct answer+x-
=+ - correct answer-x-
You need a common denominator
(U can simplify fractions to get a common denominator if possible!) - correct
answerAdding or Subtracting fractions
no special rule, just multiply Ex: 2/5 x 3/9= 6/45 - correct answerMultiplying fractions
flip 2nd fraction and multiply Ex: 2/5 divided by 3/9= 2/5 x 9/3 - correct answerDividing
fractions
either multiply both sides of the equation by the reciprocal (reciprocal is just the fraction
flipped) of the fraction, or multiply both sides of the equation by the denominator of the
fraction - correct answerSolving Equations w/ fractions
Formula: amount of change/ original number. Ex: Find the percent decrease if the price
changes from $60 to $39. 60-39= 21. amount of change= $21 original number= $60.
$21/$60= 0.35. Convert to percents. 0.35= 35% - correct answerPercent Increase or
Decrease problems
Formula: interest= principal x rate x time (I= PxRxT)
(Principal is the regular number, rate is the percent or decimal, and time is the number
representing the time in the question) - correct answerInterest
-A point has no dimension
-It is represented by a dot
, -A point is written using an upper-case letter - correct answerPoint
Has one dimension
-Named using any two point on a line w a two sided arrow above them
-It can also be named using a lower-case cursive letter - correct answerLine
Points that are on the same line - correct answerCollinear Points
Has two dimensions
-It is represented by a shape that looks like a floor or a wall, but it extends w/o an end
-Through any three points not on the same line there is exactly one plane
-A plane is written using 3 non-collinear points or with upper-case cursive letter - correct
answerPlane
Points that lie in the same plane - correct answerCoplanar points
Is named using both end points with a line above them - correct answerLine Segment
Is named using its endpoint first and then any other point on the ray pointing to the right
above them - correct answerRay
2 lines that share exactly one point - correct answerIntersecting lines
2 lines that are always the same distance apart and never touch - correct
answerParallel lines
The relationship between 2 lines which meet at a right angle (90degrees). Perpendicular
lines= 2 lines intersect at a right angle - correct answerPerpendicular lines
90 degrees - correct answerRight angle
180 degrees - correct answerStraight angle
between 0 degrees and 90 degrees - correct answerAcute angle
between 90 degrees and 180 degrees - correct answerObtuse angle
2 angles that have the sum of 90 degrees - correct answerComplementary angles
2 angles that have the sum of 180 degrees - correct answerSupplementary angles
180 degrees - correct answerthe sum of the angle measures in a triangle
All angles are acute - correct answerAcute triangle
One angle is right - correct answerRight triangle
(Updated 2025/2026)
(parenthesis, exponents, multiplication, division, addition, subtraction) work left to right -
correct answerPEMDAS
Ex: 6^4, 2^3, 9^10, etc. - correct answerExponential Notation
Ex: 7x7x7, 6x6, 2x2x2x2x2, etc. - correct answerExpanded Form
Ex: 5^2= 25; 25 is the standard notation (the answer or solution) - correct
answerStandard Notation
=+ - correct answer+x+
=- - correct answer+x-
=+ - correct answer-x-
You need a common denominator
(U can simplify fractions to get a common denominator if possible!) - correct
answerAdding or Subtracting fractions
no special rule, just multiply Ex: 2/5 x 3/9= 6/45 - correct answerMultiplying fractions
flip 2nd fraction and multiply Ex: 2/5 divided by 3/9= 2/5 x 9/3 - correct answerDividing
fractions
either multiply both sides of the equation by the reciprocal (reciprocal is just the fraction
flipped) of the fraction, or multiply both sides of the equation by the denominator of the
fraction - correct answerSolving Equations w/ fractions
Formula: amount of change/ original number. Ex: Find the percent decrease if the price
changes from $60 to $39. 60-39= 21. amount of change= $21 original number= $60.
$21/$60= 0.35. Convert to percents. 0.35= 35% - correct answerPercent Increase or
Decrease problems
Formula: interest= principal x rate x time (I= PxRxT)
(Principal is the regular number, rate is the percent or decimal, and time is the number
representing the time in the question) - correct answerInterest
-A point has no dimension
-It is represented by a dot
, -A point is written using an upper-case letter - correct answerPoint
Has one dimension
-Named using any two point on a line w a two sided arrow above them
-It can also be named using a lower-case cursive letter - correct answerLine
Points that are on the same line - correct answerCollinear Points
Has two dimensions
-It is represented by a shape that looks like a floor or a wall, but it extends w/o an end
-Through any three points not on the same line there is exactly one plane
-A plane is written using 3 non-collinear points or with upper-case cursive letter - correct
answerPlane
Points that lie in the same plane - correct answerCoplanar points
Is named using both end points with a line above them - correct answerLine Segment
Is named using its endpoint first and then any other point on the ray pointing to the right
above them - correct answerRay
2 lines that share exactly one point - correct answerIntersecting lines
2 lines that are always the same distance apart and never touch - correct
answerParallel lines
The relationship between 2 lines which meet at a right angle (90degrees). Perpendicular
lines= 2 lines intersect at a right angle - correct answerPerpendicular lines
90 degrees - correct answerRight angle
180 degrees - correct answerStraight angle
between 0 degrees and 90 degrees - correct answerAcute angle
between 90 degrees and 180 degrees - correct answerObtuse angle
2 angles that have the sum of 90 degrees - correct answerComplementary angles
2 angles that have the sum of 180 degrees - correct answerSupplementary angles
180 degrees - correct answerthe sum of the angle measures in a triangle
All angles are acute - correct answerAcute triangle
One angle is right - correct answerRight triangle
