Maths Formulas
Your complete reference guide to all the key maths formulas needed for the 11 Plus exam.
Area of Rectangle
Multiply the length by the width to find the area. Units are always squared (e.g., cm2).
Area of Triangle
Multiply the base by the height, then divide by 2. The height must be perpendicular to the base.
Area of Circle
Multiply pi (3.14159) by the radius squared. Remember: radius is half the diameter.
Perimeter of Rectangle
Add the length and width together, then multiply by 2.
Circumference of Circle
Multiply 2 by pi by the radius, or simply multiply pi by the diameter.
Volume of Cuboid
Multiply all three dimensions together. Units are always cubed (e.g., cm3).
Mean Average
Add up all the numbers, then divide by how many numbers there are.
Percentage of a Number
Divide the part by the whole, then multiply by 100 to get the percentage.
Speed, Distance, Time
Distance = Speed x Time. Time = Distance / Speed. Remember the triangle: D on top, S and T on the bottom.
Converting Fractions to Decimals
For example, 3/4 = 3 divided by 4 = 0.75. To convert to percentage, multiply by 100.