The cost of 3.5 litres of milk is 4 pounds 90. Work out the cost of 2.75 litres of milk.
We’re told in the question that 3.5 litres cost 4 pounds 90. With any question like this, our first step is to scale down to work out the cost of one unit, in this case one litre of milk. To get from 3.5 litres to one litre, we need to divide by 3.5. Whatever we do to one side of the equation, we have to do to the other. Therefore, we need to divide 4 pounds 90 by 3.5. Typing this into the calculator gives us an answer of 1.4. This is the same as one pound and 40 pence. One litre of milk costs one pound and 40 pence.
We were asked to work out the cost of 2.75 litres of milk. One multiplied by 2.75 is equal to 2.75. Therefore, we need to multiply one pound 40 by 2.75. Typing this into the calculator gives us an answer of three pounds and 85 pence.
If 3.5 litres of milk cost 4 pounds 90, then 2.75 litres will cost three pounds 85. Once you’ve completed the question, it is important to check that you answer is sensible. The number of litres of milk has decreased. As the price has also decreased, our answer is sensible.