A sum of money at a certain rate per annum of simple interest doubles in the 5 years and at a different rate becomes three times in 12 years. The lower rate of interest per annum is
Options:
A . 20%
B . 15%
C . 16$2/3$%
D . 15$3/4$%
Answer: Option C Answer: (c)The sum gets doubled in 5 years and tripled in 12 years.Clearly rate of interest for 12 years will be lower.Let Principal be x.then, Rate = ${SI × 100}/\text"Principal × Time"$= ${2x × 100}/{x × 12} = 50/3 = 16{2}/3%$Using Rule 3,$R_1 = {(2 - 1)}/5 × 100%$ = 20%$R_2 = {(3 - 1)}/12 × 100% = 16{2}/3%$Lower rate of interest =16$2/3%$
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