financial · Year 7 · Suggested learning sequence

Best buy (unit price)

The best value isn't always the cheapest pack — a bigger pack costs more but might be cheaper for the same amount. To compare fairly, work out the unit price: how much it costs per 100 g. Divide the price (in cents) by how many 100 g lots the pack holds. A 500 g pack for 400 c is 400 ÷ 5 = 80 c per 100 g. Whichever pack has the lower cents per 100 g is the better value.

Sample questions

Oats: pack A is 200 g for $1.02, pack B is 500 g for $3.10. Which is better value? Give the cheaper unit price in cents per 100 g.

  1. Pack A: 200 g is 2 lots of 100 g, so 102 ÷ 2 = 51 c per 100 g.
  2. Pack B: 500 g is 5 lots of 100 g, so 310 ÷ 5 = 62 c per 100 g.
  3. Pack A is better value at 51 c per 100 g.

Answer: 51

Pasta: pack A is 300 g for $3.00, pack B is 400 g for $1.76. Which is better value? Give the cheaper unit price in cents per 100 g.

  1. Pack A: 300 g is 3 lots of 100 g, so 300 ÷ 3 = 100 c per 100 g.
  2. Pack B: 400 g is 4 lots of 100 g, so 176 ÷ 4 = 44 c per 100 g.
  3. Pack B is better value at 44 c per 100 g.

Answer: 44

Coffee: pack A is 200 g for $1.94, pack B is 500 g for $3.70. Which is better value? Give the cheaper unit price in cents per 100 g.

  1. Pack A: 200 g is 2 lots of 100 g, so 194 ÷ 2 = 97 c per 100 g.
  2. Pack B: 500 g is 5 lots of 100 g, so 370 ÷ 5 = 74 c per 100 g.
  3. Pack B is better value at 74 c per 100 g.

Answer: 74

Practise this free in Maths Legend →