1. Substitution 3.

2. Using A Formula. What is the formula for the area of a rectangle ? l b
Area = length x breadth
A = l b
Calculate the area if l = 6 and b = 4
A = l b
We have used a formula by substituting numbers into a given expression.
l = 6
b = 4
A = 6 x 4
= 24

3. Example 1.
If R = D + T calculate R when D= 21 and T = 14.
Solution.
R = D + T
D = 21
T = 14
R =
21 + 14
R = 35

4. Example 2.
If f = g x k calculate f when g = 14 and k = 20.
Solution.
f = g x k
g = 14
k = 20
f =
14 x 20
R = 280

5. Example 3.
If W = 4  T calculate W when T= 10.
Solution.
W = 4  T
T = 10
 = 3.14
W = 4 x 3.14 x 10
W = 125.6