Correct Answer - Option 1 : 144
Given:
The ratio of the number of students in three classes is 4 : 7 : 5
Calculation:
Let be assume students in P, Q, and R is 4x, 7x, and 5x respectively.
⇒ 7x + 17 = 80
⇒ x = 9
⇒ The total number of students in all three classes = 9 × (4 + 7 + 5) = 144
∴ The required result will be 144.