Question

1. At what rate per cent per annum will $4000 yield an interest of $410 in 2 years?

2. Simple interest on a sum of money at the end of 5 years is 4/5 of the sum itself. Find the rate per cent p.a.

Answer 1

1) p=  $4000 , t = 2 , i = 410
   (p× t×r)/100 = 410
⇒(4000×2×r) /100   = 410
⇒80 r    = 410
 ⇒ r =5 (nearly 5.2)
rate =5%
2) t = 5 ,I = 4/5 p
     (p t r) /100
⇒  (p ×5 ×r) /100 = 4/5 p
⇒ pr  = 20× 4/5 p
⇒pr = 16 p
⇒ r = 16
rate of interest = 16%