The cost of 15 metres of a cloth is Rs 981.
Question:

The cost of 15 metres of a cloth is Rs 981. What length of this cloth can be purchased for Rs 1308?

Solution:

Let the length of cloth be x m. Then, we have:

 Length of cloth (in metres) 15 x Cost of cloth (in rupees) 981 1308

Clearly, more length of cloth can be bought by more amount of money.

So, this is a case of direct proportion.

Now, $\frac{15}{981}=\frac{x}{1308}$

$\Rightarrow x=\frac{15 \times 1308}{981}$

$\Rightarrow x=20$

Therefore, 20 m of cloth can be bought for Rs 1,308.