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Percentage · annual interest
P6 · Percentage · PSLE Maths
Question
Raju deposited some money in a bank at an annual interest rate of 4%. After one year, he received $96 as interest. How much money did Raju deposit at first? What was the total amount after one year?
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Hint
Treat the principal as 100%. The interest is 4% of the principal, so 4% = $96.
Show the answer and step-by-step explanation
Answer: Deposit at first 2400 $; Total amount 2496 $
- Draw the bar — The money deposited is the principal. We treat the principal as 100%. The one-year interest is 4% of the principal, so the total after one year is 104%.
- Find 4% — The question says the one-year interest is $96. This is exactly 4% of the principal.
- Find 1% — To find 100%, first divide 4% into 4 equal parts. 1% is $96 ÷ 4 = $24.
- Find principal — The principal is 100%. So the principal = 100 × $24 = $2400.
- Find total — The total amount after one year = principal + interest. $2400 + $96 = $2496. 📌 Key idea: in interest questions, treat the principal as 100%. If a certain percent is given, find 1% first, then find the required percentage.
Method: Annual interest = principal × annual interest rate. In a percentage bar model, the principal is 100%; when the interest is given, find 1% first, then find 100% and 100% + the rate.
Practice: 3 similar questions
- Siti deposited some money in a bank at an annual interest rate of 5%. After one year, she received $75 as interest. How much did Siti deposit at first? What was the total amount after one year?
Answer
1500 $, 1575 $ — 5% = $75. 1% = $75 ÷ 5 = $15. Principal 100% = 100 × $15 = $1500. Total amount = $1500 + $75 = $1575.
- Ali deposited $3200 in a bank at an annual interest rate of 2.5%. How much interest would he receive after one year? What was the total amount?
Answer
80 $, 3280 $ — 100% = $3200, so 1% = $3200 ÷ 100 = $32. Interest 2.5% = 2.5 × $32 = $80. Total amount = $3200 + $80 = $3280.
- Mei Ling deposited some money in a bank at an annual interest rate of 3.5%. After one year, the total amount was $3105. How much did Mei Ling deposit at first? How much interest did she receive?
Answer
3000 $, 105 $ — The principal is 100% and the interest is 3.5%, so the total amount is 103.5%. 103.5% = $3105, so 1% = $3105 ÷ 103.5 = $30. Principal 100% = 100 × $30 = $3000. Interest 3.5% = 3.5 × $30 = $105.
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