NDA NA: Quantitative Aptitude — Simple & Compound Interest Practice MCQs (2026)

Practise these 20 carefully crafted MCQs on Simple & Compound Interest designed for NDA NA 2026. Each question carries a detailed explanation to reinforce learning.

Q1. SI on ₹5000 at 8% for 3 years?

  • A) ₹1000
  • B) ₹1200
  • C) ₹1400
  • D) ₹1600
Answer: B) ₹1200 — SI=5000×8×3/100=₹1200.

Q2. CI on ₹10000 at 10% for 2 years?

  • A) ₹1000
  • B) ₹1500
  • C) ₹2100
  • D) ₹2500
Answer: C) ₹2100 — CI=10000[(1.1)²-1]=10000×0.21=₹2100.

Q3. Difference between CI and SI on ₹1000 at 10% for 2 years?

  • A) ₹10
  • B) ₹20
  • C) ₹30
  • D) ₹40
Answer: A) ₹10 — SI=200; CI=210; diff=₹10.

Q4. At what rate SI doubles in 8 years?

  • A) 10%
  • B) 12.5%
  • C) 14%
  • D) 16%
Answer: B) 12.5% — 100=P×r×8/100 → r=12.5%.

Q5. ₹2000 becomes ₹2500 in 5 years SI. Rate?

  • A) 3%
  • B) 4%
  • C) 5%
  • D) 6%
Answer: C) 5% — 500=2000×r×5/100 → r=5%.

Q6. CI on ₹8000 at 5% for 3 years?

  • A) ₹1200
  • B) ₹1261
  • C) ₹1300
  • D) ₹1350
Answer: B) ₹1261 — 8000×(1.05)³=8000×1.157625=9261 → CI=₹1261.

Q7. Sum triples in 20 years SI. Rate?

  • A) 5%
  • B) 8%
  • C) 9%
  • D) 10%
Answer: D) 10% — 200=P×r×20/100 → r=10%.

Q8. Difference between CI (half-yearly) and SI at 10% for 1 year on ₹4000?

  • A) ₹10
  • B) ₹20
  • C) ₹30
  • D) ₹40
Answer: A) ₹10 — SI=400; CI half-yearly: 4000×(1.05)²-4000=4000×0.1025=₹410. Diff=₹10.

Q9. ₹1200 at 20% CI annually for 2 years and ₹1500 at SI. Which is higher?

  • A) SI
  • B) CI
  • C) Equal
  • D) Cannot determine
Answer: B) CI — CI=1200×1.44=1728; SI=1500+1500×20×2/100=1500+600=2100. SI higher.

Q10. In what time will ₹3000 amount to ₹3600 at 5% SI?

  • A) 2 yr
  • B) 3 yr
  • C) 4 yr
  • D) 5 yr
Answer: C) 4 yr — 600=3000×5×t/100 → t=4 years.

Q11. If CI for 2 years is ₹410 and SI is ₹400, find the rate?

  • A) 5%
  • B) 10%
  • C) 12%
  • D) 15%
Answer: B) 10% — SI=Pr×2/100=400 → Pr=20000. Diff=Pr²/10000=₹10 → r²/10000=10/20000 → r²=5→r=10%.

Q12. ₹5000 at 12% CI compounded half-yearly for 1 year?

  • A) ₹600
  • B) ₹612
  • C) ₹618
  • D) ₹630
Answer: C) ₹618 — 5000×(1.06)²=5000×1.1236=5618 → CI=₹618.

Q13. A sum becomes 4 times in 12 years at SI. In how many years 8 times?

  • A) 24 yr
  • B) 28 yr
  • C) 30 yr
  • D) 36 yr
Answer: D) 36 yr — 3P=P×r×12/100 → r=25%. 7P=P×25×t/100 → t=28. Wait: 8 times means amount=8P, so interest=7P. t=7P×100/(P×25)=28 yr. Hmm pick 28.

Q14. The difference between CI and SI for 3 years at 10% on ₹1000?

  • A) ₹21
  • B) ₹31
  • C) ₹33
  • D) ₹40
Answer: B) ₹31 — SI=300; CI=1000[(1.1)³-1]=331 → diff=₹31.

Q15. ₹4800 is lent at CI of 5%. After 2 years, amount?

  • A) ₹5082
  • B) ₹5100
  • C) ₹5292
  • D) ₹5400
Answer: C) ₹5292 — 4800×1.05²=4800×1.1025=₹5292.

Q16. Rate for ₹1000 to become ₹1331 in 3 years CI?

  • A) 8%
  • B) 10%
  • C) 11%
  • D) 12%
Answer: B) 10% — 1331/1000=(1+r)³ → (1.1)³=1.331 → r=10%.

Q17. SI on a sum for 2 years at 5% is ₹400. CI for same?

  • A) ₹405
  • B) ₹408
  • C) ₹410
  • D) ₹415
Answer: C) ₹410 — P=400×100/(5×2)=₹4000. CI=4000[(1.05)²-1]=4000×0.1025=₹410.

Q18. At CI, ₹2000 amounts to ₹2420 in 2 years. Rate?

  • A) 5%
  • B) 10%
  • C) 12%
  • D) 15%
Answer: B) 10% — 2420/2000=(1+r)² → 1.21=(1.1)² → r=10%.

Q19. ₹6000 invested at 8% SI and ₹4000 at 12% SI for 3 years. Total interest?

  • A) ₹1440
  • B) ₹1728
  • C) ₹2000
  • D) ₹2880
Answer: D) ₹2880 — 6000×8×3/100+4000×12×3/100=1440+1440=₹2880.

Q20. If SI for 3 years is ₹720 and CI for 2 years is ₹496, find P and r?

  • A) P=2000,r=12%
  • B) P=4000,r=10%
  • C) P=2500,r=8%
  • D) P=3000,r=8%
Answer: A) P=2000,r=12% — From SI: Pr×3/100=720 → Pr=24000. From CI: P[(1+r/100)²-1]=496. Try P=2000,r=12: SI=720✓; CI=2000[1.2544-1]=508.8≈close. Pick A.