15 note books can be bought for ₹ 240. The number of note books that can be bought for ₹ 160 is:

1. 16

2. 10

3. 18

4. 15

Let x notebooks cost ₹ 160.

Since it is a case of direct variation,

$\therefore \dfrac{15}{240} = \dfrac{x}{160}\\[1em] \Rightarrow x = \dfrac{15 \times 160}{240}\\[1em] \Rightarrow x = \dfrac{2,400}{240}\\[1em] \Rightarrow x = 10$

Hence, option 2 is the correct option.