A shopkeeper gives one kite free to a customer on purchase of 24 kites. If he doubles the discount, how many kites should he give free on purchase of 69 kites?

6

No. of kites free = 1

No. of kites sold = 24 + 1 = 25

Sale = 25 kites (constant)

ATQ, shopkeeper did not increase sale but double the discount only.

It means no. of articles sale will be 25 kites but he gives 2 kites free instead of 1.

Therefore, 

on selling 25 kites, free kites = 2

on selling 75 kites, free kites = 6

Hence, on purchase of 69 kites, 6 kites will be free.