2 classes of 21 students each 21 × 2 classes = 42 students in total 42 × 3 mins = 126 minutes for 42 students 10 mins for 2 class pics = 20 minutes 126 + 20 = 146 minutes = 2 hours and 26 minutes
It should take 146 minutes (2 hours and 26 minutes) to take all the pictures.
