100-60=40. This means that 40% of the students are girls (Assuming there is no ppl that identify as anything else). If that 40% is 12 ppl, 10% in 12/4=3. 3*10=30, there are 30 ppl in the club.
You would have to get the container and put water in it but the container has to hold more than 1 liter so you would see where the water is at the measured point.
