RatioStructured · 5 marks

There were some oranges in Basket X and Basket Y. Mei took out 16 of the oranges from Basket X and put them into Basket Y. As a result, the ratio of the number of oranges in Basket X to the number of oranges in Basket Y became 4 : 7. There were then 150 more oranges in Basket Y than in Basket X.

What was the ratio of the number of oranges in Basket X to the number of oranges in Basket Y at first?
How many oranges were there in Basket Y at first?

Need a hint?

Find the number of oranges in each basket after the move first, using the 3 units that show the difference. Then work back to the amount moved.

Worked answer

(a) After the move, the difference of 7 - 4 = 3 units is 150 oranges.
1 unit = 150 ÷ 3 = 50 oranges.
After the move, Basket X has 4 × 50 = 200 oranges and Basket Y has 7 × 50 = 350 oranges.
Mei moved 16 of the original Basket X, so 200 is 56 of the original Basket X.
Original Basket X = 200 ÷ 5 × 6 = 240 oranges, and the oranges moved = 240 ÷ 6 = 40.
(a) Original ratio X : Y = 240 : 310 = 24 : 31.
(b) Original Basket Y = 350 - 40 = 310 oranges.

Answer: 310 oranges

The mistake this question tests

Habit

Stopped at one part in ratio

Many pupils take 4 : 7 as the ratio at first, forgetting the oranges moved. Others add the 40 moved oranges to Basket Y's 350 instead of taking them away, getting 390.

How to fix it at home →

Wrong answers children often give:

390 Fraction of a remainder

There were some oranges in Basket X and Basket Y. Mei took out 16 of the oranges from Basket X and put them into Basket Y. As a result, the ratio of the number of oranges in Basket X to the number of oranges in Basket Y became 4 : 7. There were then 150 more oranges in Basket Y than in Basket X.

Worked answer

The mistake this question tests

Stopped at one part in ratio

More PSLE ratio questions

Practise PSLE ratio until the mistakes stop.