Introducing Rate

≈ 20 min

A rate compares two quantities measured in different units — kilometres and hours, rand and kilograms, litres and minutes. A rate usually answers "how much per one?"

Worked example. A car travels $240$ km in $3$ hours. Its speed is $240 \div 3 = 80$ km/h — that is, $80$ km in one hour.

Same idea for prices: if $5$ kg of potatoes costs R $30$ , the unit rate is $30 \div 5 =$ R $6$ per kg. Unit rates make "best buy" decisions easy: whichever shop has the lower price per kilogram is cheaper.

A car travels $240$ km in $3$ hours. What is its speed in km/h?

$5$ kg of potatoes costs R $30$ . What is the cost per kilogram, in rand?

A tap fills $2$ buckets every $10$ minutes at a steady rate. How many buckets does it fill in $30$ minutes?

A borehole pump delivers $200$ litres in $4$ minutes. What is its unit rate?

$50$ litres per minute

$800$ litres per minute

$4$ litres per minute

$200$ litres per minute