Surd Calculations?

Surds are numbers left in 'square root form' (or 'cube root form' etc). They are therefore irrational numbers. Surds are the root of numbers and not whole numbers.

Multiplication

square root of ab = square root of a x square root of b

square root of a x square root of a = a

Example: 

√2 × √6 = √12 (= 2× 6)

= √4 × √3

= 2√3

Addition and Subtraction

4√3 - 2√3 = 2√3

5√5 + 8√5 = 13√5

Note: 5√7 + 3√3 cannot be manipulated because the surds are different (one is √7 and one is √3)

Example:

Simplify √12 + √27

12 = 3 × 4. So √12 = √(3 × 4) = √3 × √4 = 2 × √3.

Similarly, √27 = 3√3.

Hence √12 + √27 = 2√3 + 3√3 = 5√3

 

 

 

NB
Answered by Nita B. Maths tutor

12284 Views

See similar Maths GCSE tutors

Related Maths GCSE answers

All answers ▸

Solve the simultaneous equations 5x + y = 21, and x - 3y = 9.


Solve the following simultaneous equations: x^2 + y^2 = 12, x - 2y = 3


A scalene triangle has side lengths a=xcm, b=10cm and c=15cm. The angle A=105 degrees is opposite side a. Using the cosine rule, find the value of x to 3 s.f.


Solve the simultaneous equations 3x + y = 4 x + y = 2


We're here to help

contact us iconContact ustelephone icon+44 (0) 203 773 6020
Facebook logoInstagram logoLinkedIn logo

MyTutor is part of the IXL family of brands:

© 2026 by IXL Learning