Question 1 of 10 · Intermediate · free to tryPriya gave 15 marbles to her brother. She then gave 1/4 of the remaining…Priya gave 15 marbles to her…
Priya gave 15 marbles to her brother. She then gave 1/4 of the remaining marbles to her sister. She had 45 marbles left. How many marbles did she have at first?
How do you solve P5 fraction work backwards questions?
In these questions a fraction and a fixed amount are spent or given away in one or two stages, the amount at the end is given, and the start is asked.
What your child learns here
In these questions a fraction and a fixed amount are spent or given away in one or two stages, the amount at the end is given, and the start is asked. The page applies the Primary 5 fraction outcomes to working backwards.
Read the order of events: does the fixed amount go before or after the fraction?
Undo the last event first, then the one before it.
When a fraction and a fixed amount leave at the same stage, add the fixed amount back to the end amount to get the fraction that was left.
Grow that fraction to the whole by finding one part and multiplying.
Check the question: it may ask for the amount at first, the amount spent, or the cost of one stage.
Does the answer make sense?
When nothing is added along the way and the amount at first is asked, your child's answer must be more than the amount left at the end plus every fixed amount spent, given or read. When one stage's cost or the total spent is asked, it must be less than that amount at first.
How to practise these questions
Intermediate questions train undoing a single stage, including ones where the fixed amount is spent before the fraction is taken. The Challenge set stacks two stages in differing orders, adds a gain or a gift partway, or asks for one stage's cost or the total spent rather than the starting amount. If unwinding from the end feels muddled, the solution film for that question walks it back step by step; try it again later from Revision.
Questions parents ask
What does working backwards mean in fraction questions? It means starting from the amount at the end and undoing each event in reverse order until you reach the amount at first. A fixed amount is added back, and a fraction that was left is grown to the whole.
Can my child use a bar model for working backwards? Yes. A bar cut into equal parts shows the fraction, and a short extra piece shows the fixed amount. The lesson on this page draws the bar and works backwards along it.
Which syllabus outcome does this practise? It applies the Primary 5 outcome on multiplying a fraction and a whole number to word problems solved by working backwards.
