Topics › Percentage › Q103
Percent · discount and GST
P6 · Percentage · PSLE Maths
Question
Mei Ling wanted to buy a jacket at a shopping mall in Singapore. The shop first gave a 25% discount on the jacket, then charged 9% GST on the discounted price. Mei Ling then used a $10 voucher and paid $153.50. What was the marked price of the jacket?
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Hint
First add back the voucher to get the price before the voucher. This amount is 109% of the discounted price.
Show the answer and step-by-step explanation
Answer: Marked price of the jacket $200 $
- Draw marked price — Let the marked price of the jacket be 100%. After a 25% discount, 75% remains as the discounted price.
- Add back voucher — She paid $153.50 after using a $10 voucher. So the total price before the voucher was $163.50.
- Find discounted price — GST is 9% of the discounted price, so the total before the voucher is 109% of the discounted price. $163.50 corresponds to 109%.
- Work backwards — The discounted price, $150, is 75% of the marked price. So marked price = $150 ÷ 75 × 100.
- Check answer — If the marked price is $200, after a 25% discount it is $150. GST is $13.50. After subtracting the $10 voucher, the amount paid is exactly $153.50. 📌 Key idea: with discount and GST, follow the order in the question. If the final payment is given, usually add back any voucher or deduction first, then work backwards.
Method: Find the discounted price first: price with GST = 109% of the discounted price. Then use the percentage of the marked price left after the discount to work backwards.
Practice: 3 similar questions
- Raju bought a school bag at a mall. The bag was first given a 15% discount, then 9% GST was charged on the discounted price. Raju paid $92.65. What was the marked price of the bag?
Answer
$100 $ — Discounted price = 92.65 ÷ 109 × 100 = $85. After a 15% discount, 85% of the marked price remains. Marked price = 85 ÷ 85 × 100 = $100.
- Siti bought a pair of sneakers at a mall. The sneakers were first given a 20% discount, then 9% GST was charged on the discounted price. She then used a $5 voucher and paid $125.80. What was the marked price of the sneakers?
Answer
$150 $ — Total price before the voucher = 125.80 + 5 = $130.80. Discounted price = 130.80 ÷ 109 × 100 = $120. After a 20% discount, the discounted price is 80% of the marked price. Marked price = 120 ÷ 80 × 100 = $150.
- Ali bought a jacket and a water bottle at a shopping mall in Singapore. The water bottle was marked $40, with no discount, and 9% GST was charged on it. The jacket was first given a 30% discount, then 9% GST was charged on the discounted price. Ali paid $180.94 in total. What was the marked price of the jacket?
Answer
$180 $ — Price of the water bottle with GST = 40 × 109% = $43.60. Price of the jacket with GST = 180.94 − 43.60 = $137.34. Discounted price of the jacket = 137.34 ÷ 109 × 100 = $126. After a 30% discount, the discounted price is 70% of the marked price. Marked price = 126 ÷ 70 × 100 = $180.
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