Which has the lower unit price: 750 g for $4.50 or 1.2 kg for $6.60?
- Convert 750 g to 0.75 kg.
- A: 4.50 ÷ 0.75 = $6.00/kg. B: 6.60 ÷ 1.2 = $5.50/kg.
- B costs $0.50 less per kilogram.
Comparing rates
Use the same unit before choosing.
Compare on a common basis
To compare prices, calculate cost per the same unit: dollars per kilogram, not dollars per 100 g for one package and dollars per kilogram for another.
See the quantities change.
Predict before changing a value. The written explanation below remains available without JavaScript.
Decide what better means
Lower cost per kilogram is cheaper; higher pages per minute is faster. Compare the right direction and interpret it in context. A larger package is not automatically cheaper.
Keep precision until the decision
Use unrounded unit rates to decide which is lower. Round the displayed price appropriately afterward. A better unit price is not the only consideration: needed quantity, quality and waste may matter.
Khan Academy
Pause the explanation before a calculation. Predict the next step and explain which quantities are being compared.
Worked examples
Printer A makes 84 pages in 4 min. B makes 115 pages in 5 min.
- A: 84 ÷ 4 = 21 pages/min.
- B: 115 ÷ 5 = 23 pages/min.
- B is faster on these average rates.
Try it before checking.
A costs $8 for 2 kg; B costs $15 for 3 kg. Which costs less per kilogram?
A first hint
Find dollars per kilogram for each.
Compare your reasoning
A is $4/kg; B is $5/kg. A has the lower unit price.
Practise the skill.
Fresh questions · useful feedback
Build fluency, one decision at a time.
Work through eight questions. Two independent correct answers introduce a harder version; supported answers bring the next question back to the foundation. You can use hints at any time.
0 of 8 questions completed
This round saves on this device. It is practice, not a school mark.
Explain a little more.
Give a situation where the better unit price would still be a poor purchase.
Use this thinking in the If… project →