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Maths I

Formulae

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Mathematics is full of rules. In mathematics, another word for a rule is a formula. This section deals with constructing a formula, and using it to work out values. We shall also look at forming algebraic equations.

Evaluating a formula

Remember BODMAS? It means we have to work out first, the bit inside brackets, if there are any. Division and multiplication are done before addition and subtraction.

• B: Calculate anything inside brackets first.
• O: Next, work out the others (i.e. powers and square roots, etc.).
• DM: In the next step, do any division and multiplication (working from left to right)
• AS: Finally, do any addition and subtraction (working from left to right).

Example 1

A cashier used the formula below, to work out plumbers' wages.

where

• is the weekly wage.
• is the number of hours in a normal working week.
• is the hours worked in the evening.
• is the hours worked on a Saturday.

Example 2

Calculate the wages of a plumber whose normal working week is hours, and who worked hours in the evening, and hours on Saturday.

We are told , and .

Put these values into the formula:

Work inside the brackets first. Multiplication before addition

Therefore the wages are .

Now try this question.

Question

Use the formula to find the weekly wage of a plumber whose normal week is hours and who worked hours in the evening and hours on Saturday.

, ,

The wages are

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