Previous Year Questions

We know, SI = sum * rate * time/100

From statement I: An amount doubles in 4 years and triples in T years under simple interest.

Let sum = Rs. P

Then, SI = 2P - P = P * rate * 4/100

P = P * rate * (1/25)

Rate% = 25%

Now, SI = 3P - P = P * rate * T/100

2P = P * 25 * T/100

T = 8

From statement II: Simple interest received from an amount at (5T + 3)% rate of interest for 4 years is equal to the simple interest received from same amount at (4T + 12)% rate of interest for 3 years.

Let sum = Rs. P

SI = P * (5T + 3) * 4/100

And, SI = P * (4T + 12) * 3/100

Now, P * (5T + 3) * 4/100 = P * (4T + 12) * 3/100

(5T + 3) = 3 * (T + 3)

5T + 3 = 3T + 9

2T = 6

T = 3

Hence, either statement I or II alone is sufficient.