In an investment plan, if a certain sum is invested at r% per annum simple interest, it becomes ‘k’ times in 30 years, where ‘r’ and ‘k’ are natural numbers and 3 ≤ k ≤ 16. Mr. Moneylal invested
12,340 at r% per annum compounded annually for 3 years. Find the number of possible values of ‘k’ and the maximum amount that Mr. Moneylal can realize at the end of the third year.(a) 5 and
41,647.50 (b) 3 and
21,323.50(c) 5 and
38,871.50(d) 3 and
41,657.50(e) 3 and 33, 672.50(Challenging )

1) a
2) b
3) c
4) d
5) e

• S.I. = p*r*30/100
  A = P+ S.I. = kp = p+p*r*30/100 = k = 1+30r/100
  r/100 = (k-1)/3
  r/100 is max when k = 16 so substituting this we get
  r/100 = 1/2
  
  A = 12340* (1+1/2)^3 = 12340*3/2*3/2*3/2..
  A = 41647.50
• 11 years agoHelpfull: Yes(0) No(0)