math · 24 minutes · Official OETT Aligned
Material Cost
Work out how much you need to spend
What to know
- price per foot, yard, or item
- extra material allowed for waste
- adding several costs
The amount you buy must use the same unit as the price.
The core rule
Match the units, add any extra material the question asks for, then multiply by the price per unit.
If a price is per yard and a length is in inches, change inches to yards first. If the question allows 10% extra for waste, buy 110% of the needed amount. Keep full numbers during the calculation and round to cents at the end.
Worked examples
Example 1: easy
7.5 ft at $2.40/ft costs $18.00.
- The quantity and price already share feet, so multiply 7.5 ft × $2.40/ft.
- Calculate $18.00; the foot units cancel, leaving dollars.
Feet multiplied by dollars per foot gives dollars.
Example 2: medium
54 inches at $0.70/yard costs $1.05.
- Convert 54 inches to yards: 54 ÷ 36 = 1.5 yards.
- Multiply 1.5 yd × $0.70/yd = $1.05.
Convert inches to yards before using a price per yard.
Example 3: hard
120 ft plus 10% waste at $1.85/ft costs $244.20.
- Add 10% waste: 120 × 1.10 = 132 feet.
- Multiply 132 ft × $1.85/ft = $244.20.
Add the extra material before working out its cost.
Common mistakes
Multiply the given length by the price without checking units.
A price per yard needs a length in yards. Convert first.
Put it into practice
Use guided explanations, check your answers, and try a new variation.