A piggy bank contains coins of Rs. 1, Rs. 2, and Rs. 5 denominations in the strict ratio of 4:2:1. If the total monetary value of all coins in the bank is Rs. 104, what is the total number of Rs. 5 coins?

The average weight of 9 boxes is 48 kg. If one box is removed, the average weight drops to 45 kg. What is the exact weight of the removed box?

In how many distinct ways can the letters of the English word 'BIRD' be arranged to form different letter combinations?

In how many distinct ways can the letters of the English word 'BANANA' be arranged to form different letter combinations?

A 300-liter mixture contains milk and water in the strict ratio of 5:1. Exactly how many liters of water must be added to this mixture to alter the ratio to 5:4?

Two trains, A and B, are 100 meters and 110 meters long respectively. They are running on parallel tracks in opposite directions with speeds of 54 km/hr and 54 km/hr. In exactly how many seconds will they completely cross each other?

In a class of 78 students, 19 study Physics, 64 study Chemistry, and 5 study neither. How many students study both Physics and Chemistry?