Question

A car owner buys petrol at $Rs.7.50,Rs.8$ and $8.50$ per litre for three successive years. What approximately is the average cost per litre of petrol if he spends $Rs.4000$ each year?

• A. $Rs.7.98$
• B. $Rs.8$
• C. $Rs.8.50$
• D. $Rs.9$

Answer 1

The correct option is A $Rs.7.98$

Total quantity of petrol consumed in $3$ years $=(\frac{4000}{7.50}+\frac{4000}{8}+\frac{4000}{8.50})litres$
$=4000(\frac{2}{15}+\frac{1}{8}+\frac{2}{17})litres$
$=\left(\frac{76700}{51}\right)litres$
Total amount spent $=Rs.(3\times 4000)=Rs.12000$.
$\therefore$ Average cost $=Rs.\left(\frac{12000\times 51}{76700}\right)=Rs.\frac{6120}{767}=Rs.7.98$