L5 · Unit price and speed

Learning goal

“I can find a unit price to decide which of two deals is the better buy, and find a speed in kilometres per hour to compare how fast two journeys are.”

Unit price — the cost for one unit of an item: $0.80 per juice box, $3 per kilogram.

Speed — a unit rate of distance per unit of time, here kilometres per hour (km/h).

Better buy — the deal with the LOWER unit price (not always the lower sticker price, and not always the bigger pack).

Worked example

3 kg of potatoes cost $6.75. Find the unit price. Step 1: Unit price means the cost for 1 kg. Scale $6.75 : 3 kg down by 3. Step 2: 6.75 / 3 = 2.25. The unit price is $2.25 per kg. Better-buy example: Pack A is 6 pens for $4.50; Pack B is 4 pens for $3.60. Unit price A: 4.50 / 6 = $0.75 per pen. Unit price B: 3.60 / 4 = $0.90 per pen. Pack A is the better buy - each pen costs less - even though Pack A costs more in total. Never judge a deal by its sticker price or its size; judge it per 1 unit.

Check yourself — explain it

A unit price tells you...

Paired problem — example still visible

8 juice boxes cost $6.40. Find the unit price -> $0.80 per juice box

Faded completion — last step is yours

"$9 for 6 muffins is $___ per muffin" -> $1.50

Ready to practise?

10 scored questions with a 3-rung hint ladder. Mastery needs 8/10 plus both gate questions.

Start practice →Take the unit quiz