Discussion

Explanation:

Balance price to be paid in installments = Rs.1980

At the rate of r% per annum after 4 months, Rs.1980 will amount to Rs. 

$\frac{P\times R\times T}{100\times 12}$ = 1980 + $\frac{1980\times 4\times 25}{12\times 100}$ = 2145 ...(1)

Now, the total amount for the 4 installments at the end of fourth month will be $\left(x+\frac{25x+3}{12\times 100}\right)+\left(x+\frac{25x+2}{12\times 100}\right)+\left(x+\frac{25x+1}{12\times 100}\right)+x=4x+\frac{25x}{1200}(1+2+3+)=\frac{33x}{8}$ ...(2)

From (1) and (2), Rs.2145 = 33x/8

⇒ x = Rs.520

Hence, option (a).

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