Solution:

Given diameter of the cylindrical glass, d = 7 cm

Radius, r = d/2 = 7/2 = 3.5 cm

Height of the cylindrical glass, h = 12 cm

Volume of the cylindrical glass, V = r²h

= (22/7)×3.5²×12

= 462 cm³

Number of students = 1600

Milk needed for 1600 students = 1600×462

= 739200 cm³

= 739.2 litres [∵1000 cm³ = 1 litre]

Hence the amount of milk needed to serve 1600 students is 739.2 litres.