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Edexcel iGCSE (9-1) Maths > Formulae > Flashcards

Flashcards in Formulae Deck (35)
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1

Percentage change

Percentage change = (difference / original) x 100

2

Compound interest

N = Ni (1 + r/100)^n

3

Nth term of a sequence

Un = a + (n-1)d

4

Sum of a sequence where the last term is known

Sn = n/2(a + L)

5

Sum of a sequence where the last term is unknown

Sn = n/2[a + (n-1)d]

6

Equation of a straight line (3 answers)

y = mx + c

ax + by + c = 0

y - y1 = m(x - x1)

7

Area of a circle

πr²

8

Circumference of a circle (2 answers)

πd

2πr

9

Frequency density

Frequency density = frequency / class width

10

Mean

Mean = sum of values / number of values

11

Range

Range = largest value - smallest value

12

Inter-quartile range

IQR = UQ - LQ

13

Direct proportion

y ∝ x

y = kx

14

Inverse proportion

y ∝ 1/x

y = k/x

15

Probability

P = number of specified item / total number of items

16

Pythagoras’ theorem

a² + b² = c²

17

Sine rule

sin A/a = sin B/b = sin C/c

18

Cosine rule

a² = b² + c² - 2bc cosA

19

Internal intersection in a circle

AP x PB = CP x PD

20

External intersection

AP x PB = CP x PD

21

Density

d = m/V

22

Average speed

v = s/t

23

Pressure

p = F/A

24

Quadratic formula

x = [-b ± √(b² - 4ac)]/2a

25

The discriminant

b² - 4ac

26

Volume of a sphere

V = 4/3(πr^3)

27

Surface area of a sphere

A = 4πr²

28

Volume of a cone

V = 1/3πr²h

29

Surface area of a cone

A = πrl + πr²

30

Volume of a cylinder

V = πr²h

31

Surface area of a cylinder

A = 2πr² + 2πrh

32

Area of a triangle

A = 1/2 ab sinC

33

Area of a trapezium

A = ((a+b)h)/2

34

Scale factor for area

SFlength ²

35

Scale factor for volume

SFlength^3