CAT (QA) PYQs

A shop wants to sell a certain quantity (in kg) of grains. It sells half the quantity and an additional 3 kg of these grains to the first customer. Then, it sells half of the remaining quantity and an additional 3 kg of these grains to the second customer. Finally, when the shop sells half of the remaining quantity and an additional 3 kg of these grains to the third customer, there are no grains left. The initial quantity, in kg, of grains is

A donation box can receive only cheques of Rs. $100$, Rs. $250$, and Rs. $500$. On one good day, the donation box was found to contain exactly $100$ cheques amounting to a total sum of Rs. $15250$. Then, the maximum possible number of cheques of Rs. $500$ that the donation box may have contained, is

John gets Rs $57$ per hour of regular work and Rs $114$ per hour of overtime work. He works altogether $172$ hours and his income from overtime hours is $15\%$ of his income from regular hours. Then, for how many hours did he work overtime?