# Video: Solving Word Problems Involving Ratios

An irrigation machine uses 1.5 litres of fuel every 3 hours. How many litres will the machine use in 5 hours?

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### Video Transcript

An irrigation machine uses 1.5 litres of fuel for every three hours. How many litres will the machine use in five hours?

We’re told in the question that, in three hours, the irrigation machine uses 1.5 litres of fuel. We’re asked to calculate the number of litres used in five hours. A sensible start point here would be to calculate how much fuel is used in one hour.

To get from three hours to one hour, we divide by three. This means, to calculate the amount of fuel, we need to divide 1.5 litres by three. 1.5 divided by three is equal to 0.5. We know this as 15 divided by three equals five. And using our knowledge of place value, 1.5 divided by three must therefore be equal to 0.5.

As we now know the amount of fuel used in one hour, we can calculate the amount used in five hours by multiplying by five. We need to calculate 0.5 multiplied by five. Once again, we know that five multiplied by five is equal to 25. This means that 0.5 multiplied by five must be equal to 2.5.

We can therefore conclude that if the irrigation machine uses 1.5 litres of fuel in three hours, it will use 2.5 litres in five hours.