Algebraic terms and expressions : Algebraic terms and expressions Lesson objective:
To be able:
to understand and use formulae
[Level 5] Key words:
formulae Starter:
Write down some words for the meaning of the following:
a) Variable b) Term, c) Expression
Slide 2: Variable: A symbol(letter) for a number that
we do not know yet. e.g. x, y , n, t. Term: An algebraic quantity
with variables and numbers . e.g. 3x, n/2, y2 Expression: A combination of variables,
numbers and signs. e.g. 8-n, 2x-3, 2y+7-t
Identify the variable, term and expression… : Identify the variable, term and expression… Variable Term 4x – 7 = 5 Expression
Slide 4: What is formula???? Formula is a rule which helps you to calculate some quantity.
Slide 5: Example 6.3
The cost of hiring a hall for a wedding is £200 plus £6 per person. Find the formula/rule to calculate the cost. The cost (c) for 1 person is The cost (c) for 2 people is The cost (c) for 3 people is The cost (c) for n people is …… 200+6x1 200+6x2 200+6x3 200+6xn
Slide 6: Therefore, the rule, written as a formula is:
c = 200 + 6n,
where c = cost in £
n = number of people
Slide 7: Use the formula c = 200 + 6n to calculate the cost of a wedding with 70 people. Cost = c = 200 + 6 x 70 = 200 + 420 = £620
Work in pairs… : Work in pairs… c = 2 x h D = J + 40 c = 3+2x5=13 c = 3+2x3=9 c = 3+2x8=19 c = 8+5x1=13 c = 8+5x3=23 c = 8+5x7=43
Plenary : Plenary s = number of sweets in the box If I add 2 how many?
s + 2
If I add 4 more, how many?
s + 2 + 4 = s + 6
If I then eat 10, how many?
s + 6 – 10 = s – 4
How many in 2 boxes?
s + s = 2 x s = 2s
How many in 11 boxes?
11 x s = 11s
How many in 3 boxes, then I eat 7?
3s -7