Rahul borrowed a certain sum from Harish at a certain rate of simple interest for 2 years He lent th...........

Explanation:

Let sum be x.
Simple interest on x for 2 years = Rs.2000
SI= P*R*T/100
=> 2000= x*R*2/100
=> 100000=xR——-(1)
Compound Interest on x for 2 years = 2400 P(1+R/100)^t – P = 2400
=>x(1+R/100)^2 – x = 2400
=> 2xR/100 + xR^2/100 = 2400——(2)
On substituting (1) and (2), we get
R = 40%

Hence, option 3 is the correct answer.