Video: Pack 1 • Paper 2 • Question 6

Pack 1 • Paper 2 • Question 6

02:39

Video Transcript

Joshua mixes 200 millilitres of syrup A and 200 millilitres of syrup B to make 400 millilitres of syrup. Syrup A has a sugar concentration of 1.25 kilograms per litre. Syrup B has a sugar concentration of 0.8 kilograms per litre. Work out the sugar concentration of Joshua’s syrup.

Notice how the units for sugar concentration are kilograms per litre. That means we must make sure our answer is also in this form. To calculate the sugar concentration, we’re first going to need to find out how much sugar is in 200 millilitres of syrup A and 200 millilitres of syrup B.

Let’s start with syrup A. Syrup A has a concentration of 1.25 kilograms of sugar per litre. To find the amount of sugar that will be in 200 millilitres, let’s think about how many litres this is. One litre is 1000 millilitres. We can therefore divide 200 by 1000 to give us that 200 millilitres is the same as 0.2 litres. In 200 millilitres of syrup A then, we can multiply 1.25 by 0.2 to see that there is 0.25 kilograms of sugar in 200 millilitres of syrup A.

We can do the same for syrup B. 0.8 multiplied by 0.2 is equal to 0.16. There are 0.16 kilograms of sugar in 200 millilitres of syrup B. 0.25 plus 0.16 is 0.41. That means there’s a total of 0.41 kilograms of sugar in the 400 millilitres of syrup that Joshua has mixed.

Remember we said our answer should be in kilograms per litre. Currently, there are 0.41 kilograms of sugar per 400 millilitres. To change this into litres, we’ll reverse the process of earlier. We can divide by 0.4 which gives us 1.025 kilograms of sugar per 1000 millilitres, which we now know is the same as a litre.

The sugar concentration of Joshua’s syrup is 1.025 kilograms per litre.

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