Need To Know Equations

Question 1

Percentage change

Answer 1

%change= actual change/original amount *100

Question 2

Compound interest after multiple changes

Answer 2

Original*d^n

Question 3

Sum of interior angles =

Answer 3

(Number of sides - 2)*180

Question 4

Sum of exterior angles =

Answer 4

360

Question 5

For regular polygons, each exterior angle =

Answer 5

360/number of sides

Question 6

Pythagoras’ theorem

Answer 6

A^+B^2=C^2

Question 7

Gradient

Answer 7

Change in y/Change in x

Question 8

Midpoints

Answer 8

(X1 + X2 /2 , Y1+Y2/2)

Question 9

Distance between points

Answer 9

(Change in x, change in y)

Question 10

Quadratic graphs

Answer 10

y=ax^2+bx+c

Question 11

Cubic graphs

Answer 11

y=ax^3

Question 12

Reciprical graphs

Answer 12

y=a/x

Question 13

Circle graphs

Answer 13

x^2+y^2=r^2

Question 14

Area of triangle

Answer 14

1/2baseperpendicular height

Question 15

Area of a parallelogram

Answer 15

Base*perpendicular height

Question 16

Area of a trapezium

Answer 16

a+b/2*h

Question 17

Volume of pyramid

Answer 17

1/3abh

Question 18

Volume of cone

Answer 18

1/3🥧r^2*h

Question 19

Volume of a prism

Answer 19

Cross sectional area * height

Question 20

Volume of a sphere

Answer 20

4/3🥧r^3

Question 21

Volume of hemisphere

Answer 21

2/3🥧r^3

Question 22

Area of a kite

Answer 22

1/2LW

Question 23

Area of a sector

Answer 23

Angle of sector/360 * area of circle

Question 24

Surface area of a cylinder

Answer 24

2🥧r^2 + 2🥧rh

Question 25

Surface area of a sphere

Answer 25

4🥧r^2

Question 26

Surface area of a cone

Answer 26

🥧r^2 + 🥧rl

Question 27

Frequency density

Answer 27

= frequency/class width

Question 28

Sine rule for lengths

Answer 28

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

Question 29

Sine rule for angles

Answer 29

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

Question 30

Cosine rule for lengths

Answer 30

a2 = b2+c2 - 2(b)(c) cos (A)

Question 31

Cosine rule for angles

Answer 31

Cos A = b2+c2-a2 / 2(b)(c)