A sum borrowed under simple interest doubles itself in 10 years. When will it…
2024
A sum borrowed under simple interest doubles itself in 10 years. When will it become fourfold of itself at the same rate of interest?
Answer: C. 30 — Correct Answer: 30 years Let the principal be P. For simple interest: SI = (P × R × T) / 100 Since the sum doubles in 10 years: P + (P × R × 10) / 100 = 2P ⇒…
- A.
15
- B.
40
- C.
30
- D.
20
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Correct answer: C
Correct Answer: 30 years
Let the principal be P.
For simple interest:
SI = (P × R × T) / 100
Since the sum doubles in 10 years:
P + (P × R × 10) / 100 = 2P
⇒ (P × R × 10) / 100 = P
⇒ R × 10 / 100 = 1
⇒ R = 10% per annum
To become fourfold:
P + (P × R × T) / 100 = 4P
⇒ (P × R × T) / 100 = 3P
⇒ R × T = 300
With R = 10,
10 × T = 300
⇒ T = 30 years
Therefore, the sum will become four times itself in 30 years.