WEBVTT
00:00:01.600 --> 00:00:05.480
The cost of 3.5 litres of milk is 4 pounds 90.
00:00:06.240 --> 00:00:09.880
Work out the cost of 2.75 litres of milk.
00:00:11.360 --> 00:00:15.920
We’re told in the question that 3.5 litres cost 4 pounds 90.
00:00:17.360 --> 00:00:26.480
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.
00:00:28.200 --> 00:00:33.240
To get from 3.5 litres to one litre, we need to divide by 3.5.
00:00:34.600 --> 00:00:38.000
Whatever we do to one side of the equation, we have to do to the other.
00:00:38.520 --> 00:00:42.560
Therefore, we need to divide 4 pounds 90 by 3.5.
00:00:44.280 --> 00:00:48.120
Typing this into the calculator gives us an answer of 1.4.
00:00:48.800 --> 00:00:51.760
This is the same as one pound and 40 pence.
00:00:53.080 --> 00:00:56.840
One litre of milk costs one pound and 40 pence.
00:00:58.360 --> 00:01:02.440
We were asked to work out the cost of 2.75 litres of milk.
00:01:03.760 --> 00:01:08.480
One multiplied by 2.75 is equal to 2.75.
00:01:09.200 --> 00:01:13.520
Therefore, we need to multiply one pound 40 by 2.75.
00:01:15.400 --> 00:01:20.880
Typing this into the calculator gives us an answer of three pounds and 85 pence.
00:01:21.960 --> 00:01:30.120
If 3.5 litres of milk cost 4 pounds 90, then 2.75 litres will cost three pounds 85.
00:01:31.480 --> 00:01:36.080
Once you’ve completed the question, it is important to check that you answer is sensible.
00:01:36.800 --> 00:01:39.560
The number of litres of milk has decreased.
00:01:40.520 --> 00:01:44.280
As the price has also decreased, our answer is sensible.