1.  The simple interest on a certain sum of money for 3 years at 8 % per annum is half the compound interest on ₹ 8000 for 2 years at 10 % per annum. Find the sum on which simple interest is calculated:
A. ₹ 3500
B. ₹ 3800
C. ₹ 4000
D. ₹ 3600

Answer: Option A

Explanation:

CI = 8000 x (1 + 10/100)2 - 8000
= 8000 x (11/10) x (11/10) - 8000
= ₹ 9680 - 8000
= ₹ 1680

∴ Sum = (840 x 100)/(3 x 8) = ₹ 3500
[ ∵ SI is half of CI ]
∴ SI = 1680/2 = ₹ 840