1.In how many ways can the first and second prizes in mathematics and the first and second prizes in physics be awarded in a class of 25 pupils?

In a class of 25 students, the first and second award can't be given to the same person, but a student who has received an award in maths can again receive the award for physics. 

 

So, its like choosing 2 people from the class of 25 students twice and then once these students are picked, they can again be given either first or second prize.