Q. What annual instalment will discharge a debt of 6450 Rs. due in 4 years at 5% simple interest?
Answer: 1500 Rs
Notes: Let each instalment be x. Then,
$latex \because \left ( x+\frac{x\times 5\times 1}{100} \right ) + \left ( x+\frac{x\times 5\times 2}{100} \right ) + \left ( x+\frac{x\times 5\times 3}{100} \right ) + x = 6450&s=1$
$latex => \left ( x+\frac{x}{20} \right )+\left ( x+\frac{x}{10} \right )+\left ( x+\frac{3x}{20} \right )+x = 6450&s=1$
$latex => \frac{21x}{20}+\frac{11x}{10}+\frac{23x}{20}+x = 6450&s=1$
$latex => \frac{21x+22x+23x+20x}{20} = 6450&s=1$
$latex => \frac{86x}{20} = 6450&s=1$
$latex => x = \frac{6450\times 20}{86} = 1500 Rs.&s=1$
Hence option [A] is correct answer
