Area of a triangle

Area = 1/2 x base x height

Area of a parallelogram

Area = base x height

Area of a trapezium

Area = 1/2 x (sum of parallel sides) x height

Circumference of circle

C = pi x d = 2 x pi x r (use 3.14 or 22/7)

Area of circle

Area = pi x r x r

Volume of cuboid

V = length x breadth x height

Find percentage of a number

Multiply by x/100. 25% of 80 = 80 x 0.25 = 20.

Find whole from percentage

Whole = value / (x/100). If 30%=60, whole=200.

Discount formula

Discount = Price x Discount%. Selling Price = Original - Discount.

GST calculation

Price with GST = Price x 1.09 (9% GST in Singapore).

Speed formula

Speed = Distance / Time.

Average (Mean)

Total sum / Number of items.

Fractions to decimals

Divide numerator by denominator. 3/4 = 0.75.

Decimals to percentages

Multiply by 100. 0.75 = 75%.

Simplify a ratio

Divide by HCF. 12:8 -> 3:2.

Angles on a straight line

Add up to 180 degrees.

Angles at a point

Add up to 360 degrees.

Vertically opposite angles

They are equal.

Angle sum of triangle

180 degrees.

Isosceles triangle

2 equal sides and 2 equal base angles.

Equilateral triangle

3 equal sides and 3 angles of 60 degrees each.

Angles in quadrilateral

360 degrees.

What is HCF?

Highest Common Factor. Largest number dividing two or more numbers exactly.

What is LCM?

Lowest Common Multiple. Smallest common multiple of two or more numbers.

BODMAS

Brackets, Orders, Division, Multiplication, Addition, Subtraction.