Rate = (Interest x 100) / (Principal x Time)

Correct Option: C

Rate = (Interest x 100) / (Principal x Time)
= (800 x 100) / (8000 x 2)
= 5%

S.I = Principal x Rate x Time / 100
∴ Amount - Principal = Principal x Rate x Time / 100
⇒ 5712 - 4200 = (4200 x Rate x 4) /100
⇒ 1512 = 42 x 4 x Rate
Rate = 1512 / (42 x 4) = 9%
On increasing 3%, new rate of interest = 9 + 3 = 12%

Correct Option: C

S.I = Principal x Rate x Time / 100
∴ Amount - Principal = Principal x Rate x Time / 100
⇒ 5712 - 4200 = (4200 x Rate x 4) /100
⇒ 1512 = 42 x 4 x Rate
Rate = 1512 / (42 x 4) = 9%
On increasing 3%, new rate of interest = 9 + 3 = 12%

Simple interest on new rate = (4200 x 12 x 4) / 100 =Rs. 2016
Amount = Principal + Interest = 4200 + 2016 = Rs. 6216

Let the sum be ₹ P .
Then, SI = 4P - P = ₹ 3P
(P x 12 x T)/100 = 3P

Correct Option: B

Let the sum be ₹ P .
Then, SI = 4P - P = ₹ 3P
(P x 12 x T)/100 = 3P
⇒ T = (3 x 100)/12 = 25 yr

Let the principle be ₹ P .
Then,
(P x 1 x 5)/100 + (P x 1 x 6)/100 + (P x 1 x 8)/100 = 760

Correct Option: C

Let the principle be ₹ P .
Then,
(P x 1 x 5)/100 + (P x 1 x 6)/100 + (P x 1 x 8)/100 = 760
⇒ 5P/100 + 6P/100 + 8P/100 = 760
⇒ 19P = 760 x 100
∴ P = (760 x 100)/19 = ₹ 4000
Hence, the principle is ₹ 4000.

Given, P = 18440, R = 15%, T = 4
∴ Simple interest (SI) = (P x R x T) / 100

Correct Option: E

Given, P = 18440, R = 15%, T = 4
∴ Simple interest (SI) = (P x R x T) / 100
= (4 x 18440 x 15) / 100
= ₹ 11064