Tiered charges

The table below shows the parking charges at a car park. Raju parked his car there for 3 hours 40 minutes. How much was he charged for parking? Try it first. Pause if you like. Two rows, and they charge two different things. The first hour costs 1 dollar 50 cents, on its own. After that first hour, every half hour costs 60 cents. And read the end of that row. Every half hour, or part of one. Here's the 3 hours 40 minutes, end to end. The first hour is charged on its own, so cut it off first. The rest is 3 hours 40 minutes minus one hour. 2 hours 40 minutes. Now cut the rest into half hours. One. Two. Three. Four. Five. And 10 minutes over. 10 minutes is a part of a half hour, and a part of a half hour is charged in full. So 6 half hours are charged. Write that down, and write down why. 6 half hours at 60 cents each. 3 dollars 60 cents. And the first hour was 1 dollar 50 cents. Raju was charged 5 dollars 10 cents for parking. A tariff counts blocks, not minutes. The last block was 10 minutes used and a whole block charged. Or part of one. That is what those four words on the table are for. A part of a block is a whole block.