12 welders work at a constant rate they complete an order in 8 days. If after the first day, 9 welders start to work on the other project, how many more days the remaining welders will need to complete the rest of the order? Choose the correct choice from the following answers:
A) 5
B) 12
C) 18
D) 24
E) 28

Rationale: "1 . we need to find out the time taken by 3 workers after day 1 . 2 . total no . of wokers * total time taken = time taken by 1 worker 3 . time taken by 1 worker = 12 * 8 = 96 days 4 . but on day 1 twelve workers had already worked finishing 1 / 8 of the job . so 3 workers have to finish only 7 / 8 of the job . 5 . total time taken by 3 workers can be got from formula used at ( 2 ) . i . e . , 3 * total time taken = 96 . total time taken by 3 workers to finish the complete job is 96 / 3 = 32 days . 6 . time taken by 6 workers to finish 7 / 8 of the job is 7 / 8 * 32 = 28 days . the answer is choice e"
Answer: E