Answer : Option B

Explanation :

$MF#%\text{Simple Interest = }\dfrac{\text{PRT}}{100} = \dfrac{900 \times 10 \times 1}{100} = \text{ Rs. }90$MF#%
Amount after 1 year on Rs.900 at 10% per annum when interest is reckoned half-yearly
$MF#%= \text{P}\left(1 + \dfrac{\text{(R/2)}}{100}\right)^\text{2T} = 900\left(1 + \dfrac{(10/2)}{100}\right)^{2 \times 1} = 900\left(1 + \dfrac{5}{100}\right)^{2} = 900\left(\dfrac{105}{100}\right)^{2}\\\\ = \dfrac{900\times 105 \times 105}{100 \times 100} = \text{Rs. 992.25}$MF#%
Compound Interest = 992.25 - 900 = 92.25
Required difference between simple interest and compound interest = 92.25 - 90 = Rs.2.25