RRB Group D Half-Yearly / Quarterly CI — Study Material & 3 Practice MCQs | ZestExam
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RRB Group D Half-Yearly / Quarterly CI
Study Material · Concept Notes · Shortcuts
This page covers RRB Group D Half-Yearly / Quarterly CI with complete concept notes, 3 graded practice MCQs, key points and exam-specific tips. Free to study.
When you deposit money in a bank, the bank usually adds interest once a year. But some banks add interest twice a year (half-yearly) or four times a year (quarterly). Each time interest is added, it becomes part of the new principal, and the next interest is calculated on this larger amount. This is why more frequent compounding gives you more interest
💡Key Rules
For half-yearly CI: The rate is divided by 2, and time is multiplied by 2.
For quarterly CI: The rate is divided by 4, and time is multiplied by 4
🔑Formula
A = P × (1 + R/(100×n))^(t×n)
Where:
- A = Amount after interest
- P = Principal (original money)
- R = Annual rate of interest (%)
- n = Number of times compounded per year (2 for half-yearly, 4 for quarterly)
- t = Time in years
- CI = A − P
📊
Exam Patterns
What examiners ask — read before attempting PYQs
SSC CGL typically asks: Compare CI for different compounding periods, find CI amount, or calculate effective rate.
Shortcut/Trick:
For half-yearly: Use R/2 and 2t. For quarterly: Use R/4 and 4t. Always remember the rate gets divided and time gets multiplied by the same number.
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Worked Example
Solve this step-by-step before moving on
1
Step 1
Identify n = 4 (quarterly)
2
Step 2
Apply formula: A = 8000 × (1 + 20/(100×4))^(1×4)
3
Step 3
A = 8000 × (1 + 5/100)^4
4
Step 4
A = 8000 × (1.05)^4
5
Step 5
A = 8000 × 1.2155 = 9724
6
Step 6
CI = 9724 − 8000 = Rs 1724
Common Mistake:
Students forget to divide the rate by the compounding frequency. They use the full annual rate instead of R/2 or R/4, leading to wrong answers. Always reduce the rate first.
Test Half-Yearly / Quarterly CI under exam conditions
A sum of ₹8,000 is invested at 12% per annum compound interest, compounded half-yearly. What will be the amount after 1 year?
Practice 2medium
A sum of money is invested at 12% per annum compound interest, compounded quarterly. If the compound interest earned in 6 months is ₹363, find the principal.
Practice 3hard
A sum of money is invested at 20% per annum compound interest, compounded quarterly. If the amount becomes ₹19,360 after 1.5 years, what was the principal?
60-Second Revision — Half-Yearly / Quarterly CI
Remember: Divide rate by compounding frequency (2 for half-yearly, 4 for quarterly), multiply time by the same number
Formula: A = P × (1 + R/(100×n))^(t×n) — this works for ALL compounding frequencies
Trap: Don't forget CI = Amount − Principal; calculate both separately
Quick Check: In 1 year with quarterly CI at 20% p.a., effective rate ≈ 21.55% (not 20%)
Pattern: More frequent compounding always gives MORE interest for same P, R, and t
Always verify: After substitution, ensure exponent = compounding periods per year × time in years