Simple, Compound Interest and Principal Page-3

17) Calculate the simple interest on Rs. 5640 invested for 7 months at 6% per annum.
(A) 197.40
(B) 198.50
(C) 199.60
(D) 200.70

18) A sum of money becomes double on simple interest in 20 years. It will quadruple at the same rate in
(A) 40 years
(B) 50 years
(C) 60 years
(D) 80 years