1. Substitute the values given in the following formulae to find the value of the unknown variable:
a. 
P = 2x + 2y 
Find P when x = 3 mm and y = 4 mm. This is the formula for the perimeter of a rectangle. 
b. 
V = lwh 
Find V when l = 2 m, w = 3 m and h = 6 m. This is the formula for the volume of a cuboid. Answer is in m^{3} 
c. 
A = 0.5h(a + b) 
Find A when h = 4 cm, a = 3.5 cm and b = 2.5 cm This is the formula for the area of a trapezium. Answer is in cm^{2.} 
d. 
v = ^{d}⁄_{t} 
Find v when d (distance) = 100 metres and t (time) = 10 seconds This is a formula for velocity. Answer is in metres per second. 
e.

C = 0.5F − 15 
Find C when F = 77°. This is an approximate formula for changing degrees fahrenheit to degrees centigrade. Answer is in degrees centigrade. 
f.

P = ^{V2}⁄_{R} 
Find P when V (voltage) = 12 volts and R (resistance) = 1000 ohms This is a formula for power. Answer is in watts. 
g.

F = mg 
Find F when m (mass) = 12 kg and g (accelaration due to gravity) = 10 m/s^{2}. This is a formula for force. Answer is in Newtons. 
h.

C = ^{5}⁄_{9} × (F − 32) 
Find C when F = 77° This is an precise formula for changing degrees fahrenheit to centigrade. Answer is in degrees centigrade. 
i.

I = 180 (n − 2) 
Find I when n = 10. This is the formula for the sum of the interior angles of a polygon. 
j. 
C = 2π r 
Find C when π = 3.14 and r = 4.5 cm This is a formula for the circumference of a circle. Answer is in cm. 
2. Construct a formula for the area and perimeter of the following rectangle:
3. Make a formula for the perimeter of the triangle and find the perimeter when x = 2. All measurements in centimetres.
4. Make a formula for the size of angle P in this triangle. Remember that the angles in a triangle add up to 180°
Find the size of each angle when x = 50.