Rate

A rate tells you how much of something happens for each one of something else — pages printed per minute, litres flowing per second, dollars earned per hour. You use rates without thinking: if a tap fills 2 litres every minute, you already know 5 minutes gives 10 litres. The maths just makes that thinking neat and reliable. Let's set the pace.

Parents: let your child predict before they reveal each step. The blue dotted words are tappable definitions, and the "Method tip" boxes name exactly what a PSLE marker rewards in the working — not just the final number.

By the end you'll be able to describe a rate as an amount per unit, and find the rate, the total, or the base when you know the other two. Let's begin.

Rate as an amount per unit

A rate links two quantities, with the word "per" meaning "for each one". A printer that prints 30 pages in 5 minutes has a rate of 30 ÷ 5 = 6 pages per minute. To find a rate, divide the total by the base.

The base is what comes after "per". Always reduce to "per ONE" first — that single value is what makes a rate so useful.

Finding the total from a rate

Once you know the rate, finding the total is multiplication. If a worker is paid $8 per hour and works 6 hours, the total pay is 8 × 6 = $48. The rate per one unit times the number of units gives the total.

Picture a hawker selling 15 plates of chicken rice each hour for 4 hours — that is 15 × 4 = 60 plates in total. Rate times base equals total.

Finding the base from a rate and total

The third type works backwards. You know the rate and the total, and you must find the base — the number of units. Divide the total by the rate. If a car park charges $3 per hour and a driver paid $18, then the hours parked is 18 ÷ 3 = 6 hours.

So total divided by rate gives the base. Think of it as undoing the multiplication from the last section.

Watch out — these are easily mixed up

Quick recap

🎯 Mastery check

Answer all 6 — your progress is saved on this device.

1. A tap fills 18 litres in 6 minutes. What is the rate?

   3 litres per minute24 litres per minute6 litres per minute

2. A worker earns $9 per hour. How much for 7 hours of work?

   $63$16$72

3. A printer makes 8 pages per minute. How long to print 72 pages?

   9 minutes64 minutes80 minutes

4. A hawker sells 12 bowls of soup each hour. How many bowls in 4 hours?

   48316

5. A car park charges $2 per hour. A driver pays $14. How many hours did they park?

   7 hours28 hours12 hours

6. A garden hose fills a 40-litre tank in 8 minutes. What is its rate, and how long to fill 25 litres?

   5 litres per minute, so 5 minutes8 litres per minute, so 8 minutes5 litres per minute, so 8 minutes

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