What is the interest payable on ₹12,000 for 3 months at the rate of 1…

As the interest is compounded quarterly.

So, actual rate = \(\frac{10}{4}\)% = 2.5%

Formula used here is :- 

Amount = Principal + Interest

Amount = P$(1 \;+\; \frac{R}{100})^t$

Compound interest = 12000 [ 1 +  \(\frac{2.5}{100}\) ]¹ - 12000

= 12000 [ \(\frac{41}{40}\) ]¹ - 12000

= 12300 - 12000

= Rs. 300