Find Missing number

In a class, 3/5 of the students are girls and rest are boys. If 2/9 of the girls and 1/4 of the boys are absent. What part of the total number of students are present?

$$(49)^{15}-1$$ is exactly divisible by :

one fourth of a tank holds 135 litres of water. What part of the tank is full if it contains 180 litres of water ?