At 20% per annum rate, an amount is doubled in approximately in ______ years at compound interest.

This question was previously asked in
RPF Constable 2024 Official Paper (Held On 05 Mar, 2025 Shift 3)
View all RPF Constable Papers >
  1. 2
  2. 5
  3. 4
  4. 3

Answer (Detailed Solution Below)

Option 3 : 4
Free
RPF Constable Full Test 1
3.9 Lakh Users
120 Questions 120 Marks 90 Mins

Detailed Solution

Download Solution PDF

Given:

Rate (r) = 20% per annum

Amount becomes double ⇒ A = 2P

Formula used:

A = P(1 + r/100)t

Calculation:

⇒ 2P = P(1 + 20/100)t

⇒ 2 = (1.2)t

Now, take logarithm both sides:

⇒ log(2) = t × log(1.2)

⇒ t = log(2) ÷ log(1.2)

⇒ t = 0.3010 ÷ 0.0792

⇒ t ≈ 3.8 years

∴ The amount is doubled in approximately 4 years.

Latest RPF Constable Updates

Last updated on Jul 16, 2025

-> More than 60.65 lakh valid applications have been received for RPF Recruitment 2024 across both Sub-Inspector and Constable posts.

-> Out of these, around 15.35 lakh applications are for CEN RPF 01/2024 (SI) and nearly 45.30 lakh for CEN RPF 02/2024 (Constable).

 

-> The Examination was held from 2nd March to 18th March 2025. Check the RPF Exam Analysis Live Updates Here.

More Installments Questions

More Interest Questions

Get Free Access Now
Hot Links: teen patti gold old version teen patti download apk teen patti real teen patti master apk download teen patti octro 3 patti rummy