There are two candles each of the same initial length. The first candle can burn for $24 \mathrm{hours}$, while the second candle can burn for $16 \mathrm{hours}$. Both of them are lit at the same time. After sometime, it was found that one of the candles was twice as long as the second. For how long had the candle been burning?

From each of two given numbers, half the smaller number is subtracted. Of the resulting numbers the larger one is five times as large as the smaller one. What is the ratio of the two numbers?

A stockist wants to make some profit by selling oil. He contemplates about various methods. Which of the following would maximise his profit?

$\mathrm{I}$. Sell oil at 20% profit.

$\mathrm{II}.$ Use 800 g of weight instead of 1 kg

$\mathrm{III}.$Mix 20% impurities in oil and selling it at cost price.

$\mathrm{IV}.$Increase the price by 10% and reduce weights by 10%.

$\left(\mathrm{a}\right)$$\mathrm{I} \mathrm{or} \mathrm{III}$

$\left(\mathrm{b}\right) \mathrm{II}$

$\left(\mathrm{c}\right) \mathrm{II} \mathrm{and} \mathrm{IV}$

$\left(\mathrm{d}\right)$ Profits are same