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

11620 Views

See similar Maths GCSE tutors

Related Maths GCSE answers

All answers ▸

Please explain (said question) surrounding a proof of 2 equal angles


There are green and red counters in a bag. There are 30 counters in total. The ratio of red to green counters is 1 : 5. There are 5 red counters in the bag. How many green counters are in the bag?


Factorise x^2 + 5x + 6


Five numbers have a mean of 9.4 . Four of the numbers are 3, 5, 10 and 12. Work out the range of the five numbers. ( 4 marks )


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:

© 2025 by IXL Learning