A certain sum of money becomes three times of itself in 20 years at simple interest. In how many years does it become double of itself at the same rate of simple interest ?
Options:
A . 10 years
B . 8 years
C . 14 years
D . 12 years
Answer: Option A Answer: (a)Case-ILet the principal be xAmount = 3xInterest = 2xTime = 20 yearsI = $\text"PRT"/100$2x = ${x × R × 20}/100$ ⇒ R = 10%Case-III = x, P = x, R = 10, T = ?I = $\text"PRT"/100$x = ${x × 10 × T}/100$ ⇒ T = 10 years.Using Rule 3,R% = ${(3 - 1)}/20$ × 100% = 10%Now, T = ${(n - 1)}/R$ yearsT = ${2 - 1}/10 × 100$ = 10 years
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