Given, Student can complete (1/12 th part of the work in a day ∴ Student can complete the work in 12 days. ∵ The teacher is twice as fast as the student ∴ The teacher can complete the work in 6 days. ∴ Part of work done by the teacher and the student together in a day =
1
12
+
1
6
= (1 + 2)/12 = 1/4 ∴ The teacher and student together can complete the work in 4 days