By the end of this lesson, you will be able to:
Copy these questions and work them out:
Write using algebraic conventions:
Write as algebra:
Write as algebra:
Work on these questions for 10 minutes:
Whatever you don’t finish now is homework.
Write number sentences for these expressions. Example given.
Copy this definition:
Substitution means replacing a pronumeral with a number to find the value of an expression.
Example:
If \(n = 5\), find the value of \(3n + 2\)
\(3n + 2 = 3(5) + 2 = 15 + 2 = 17\)
Copy the definition and examples
A formula is a general rule that is written as an algebraic equation and shows the relationship between variables.
Examples:
Copy
Example 1: The formula for perimeter of a rectangle is \(P = 2l + 2w\).
If a rectangle has length = 8cm and width = 5cm, find the perimeter.
The formula for area of a square is \(A = s^2\)
If a square has side length = 7m, find the area.
The total cost of my canteen order is \(C = 8n\) where \(n\) is the number of butter chickens I order.
If I order \(3\) butter chickens, what is the total cost?
The total cost of my canteen order is \(C = 8n\) where \(n\) is the number of butter chickens I order.
If I order \(3\) butter chickens, what is the total cost?
Solution:
\(C = 8n\)
\(C = 8(3)\) Remember this means \(8 \times 3\)
\(C = \$24\)
Work through these together:
If \(a = 4\) and \(b = 3\), find the value of:
\(2a + 5\)
\(3b - 1\)
\(ab\)
\(\frac{a + b}{2}\)
Work through these together:
Use \(P = 2l + 2w\) to find the perimeter when \(l = 12\) and \(w = 7\)
Use \(A = s^2\) to find the area when \(s = 9\)
Use \(C = 4.20n\) to find the cost of \(n = 5\) meat pies
Attempt these, then we’ll review:
If \(x = 6\) and \(y = 2\), find:
\(x + 4\)
\(3y\)
\(xy\)
\(2x - y\)
\(\frac{x}{y}\)
\(x^2\)
\(4x + 3y\)
\(\frac{x + y}{4}\)