In a school of 1200 students, teacher-to-student ratio is 1:15. It increases to 3:40. How many teachers joined?

In a school of 1200 students, teacher-to-student ratio is 1:15. It increases to 3:40. How many teachers joined?

Explanation

Original: 1 teacher per 15 students → 1200 ÷ 15 = 80 teachers


New ratio: 3 teachers per 40 students → (1200 ÷ 40) × 3 = 30 × 3 = 90 teachers


Teachers joined = 90 - 80 = 10