A mixed number combines a whole number and a proper fraction, such as 2 3/4, which means 2 + 3/4. Mixed numbers are easy to read and estimate but awkward to compute with, so for multiplication, division and many additions you first convert to an improper fraction. To convert, multiply the whole number by the denominator, add the numerator, and keep the same denominator. Going back, divide the numerator by the denominator: the quotient is the whole part and the remainder over the denominator is the fraction. Always simplify the fractional part at the end.
✅ Solved examples
1. Add 1 1/4 + 2 1/4.
Add the whole parts (1 + 2 = 3) and the fractions (1/4 + 1/4 = 2/4 = 1/2), giving 3 1/2.
denominator (lowest terms) has only factors 2 and 5
Recurring
any other denominator → repeating block
Compare fractions
cross-multiply or use a common denominator
Digital SAT reference
Area & Circumference
Circle area
A = πr²
Circle circumference
C = 2πr
Rectangle
A = ℓw
Triangle
A = ½ b h
Volume
Rectangular box
V = ℓwh
Cylinder
V = πr²h
Sphere
V = 4⁄3 πr³
Cone
V = 1⁄3 πr²h
Pyramid
V = 1⁄3 ℓwh
Right triangles
Pythagorean theorem
a² + b² = c²
30°–60°–90°
sides x : x√3 : 2x
45°–45°–90°
sides s : s : s√2
Constants
Degrees in a circle
360°
Radians in a circle
2π
Angles of a triangle
sum = 180°
🖩 Graphing Calculator
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