The average salary/head of allthe workers in a workshop is Rs.850, if the average salary/head of 7technician is Rs.1000 and the average salary/head of the rest is Rs.780, the total no. of workers in the work-shop is ?
Choose the correct choice from the following answers:  A) 18  B) 20  C) 22  D) 23  E) 25

Rationale: let the total number of workers be y . so sum of salary for all workers = sum of salary of 7 technician + sum of salary for other y - 7 workers . 7 x 1000 + 780 ( y - 7 ) = 850 y ⇒ 7000 + 780 y - 5460 = 850 y ⇒ 70 y = 1540 ∴ y = 22 so total number of workers = 22 c
Answer: C