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A sum of money invested at compound interest amounts to Rs 800 in 3 years and to Rs 840 in 4 years. The rate of interest per annum is
  • a)
    4%
  • b)
    5%
  • c)
    6%
  • d)
    2%
Correct answer is option 'B'. Can you explain this answer?
Verified Answer
A sum of money invested at compound interest amounts to Rs800 in 3 yea...
S.I. on Rs 800 for 1 year = Rs [840 – 800]
= Rs 40
Rate = (100 × 40/800 × 1)%
= 5%
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Most Upvoted Answer
A sum of money invested at compound interest amounts to Rs800 in 3 yea...
Given:
- The sum of money invested at compound interest amounts to Rs800 in 3 years.
- The sum of money invested at compound interest amounts to Rs840 in 4 years.

To Find:
- The rate of interest per annum.

Solution:

Let's assume the principal amount as P and the rate of interest per annum as R.

Step 1: Find the compound interest after 3 years.
- Using the formula for compound interest:
Amount = Principal + Compound Interest

- We know that the amount after 3 years is Rs800, so we can write:
Rs800 = P + Compound Interest

- Also, we know that the compound interest after 4 years is Rs840, so we can write:
Rs840 = P + Compound Interest

- Subtracting the first equation from the second equation, we get:
Rs840 - Rs800 = (P + Compound Interest) - (P + Compound Interest)
Rs40 = 0

- This is not possible, as 0 cannot be equal to Rs40. Therefore, there is some mistake or inconsistency in the given information.

As there is an inconsistency in the given information, we cannot determine the rate of interest per annum.
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A sum of money invested at compound interest amounts to Rs800 in 3 years and to Rs 840 in 4 years. The rate of interest per annum isa)4%b)5%c)6%d)2%Correct answer is option 'B'. Can you explain this answer?
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