A man purchased some eggs at 3 for rupees 13.50 and sold them at 5 for rupees 25.00. He gained rupees 50 in the transaction. How many eggs did he purchased?

cost price per egg = 13.5/3 = 4.5

selling price per egg= 25/5 = 5
profit per egg = 0.5
number of eggs ---- n
.5n = 50
n = 100 <------ He purchased 100 eggs

check:
cost price = 100(4.5) = 450
selling price = 100(5) = 500
profit = 500-450 = 50

my answer is correct