Typing work with an interruption: A report of 100 pages is to be typed by three typists. Speeds: A types 100 pages in 10 hours, B in 20 hours, and C in 25 hours. All start at 09:00 a.m. At 01:00 p.m. (after 4 hours) A stops. B and C continue and finish the job. Approximately at what time is the report completed?

Introduction / Context:
Translate times to page-per-hour speeds, compute pages typed before A leaves, then finish with the remaining two typists.

Given Data / Assumptions:

• A: 100 pages/10 h = 10 pph.
• B: 100 pages/20 h = 5 pph.
• C: 100 pages/25 h = 4 pph.
• All start 09:00; A stops at 13:00.

Concept / Approach:
Pages done till 13:00 plus remaining pages divided by the combined B + C speed gives the additional time.

Step-by-Step Solution:
First 4 hours at combined 10 + 5 + 4 = 19 pph ⇒ 4 * 19 = 76 pages done.Remaining pages = 100 − 76 = 24 pages.B + C speed = 5 + 4 = 9 pph.Time to finish = 24 / 9 = 2 h 40 m.Finish time = 13:00 + 2:40 = 15:40 ⇒ 3:40 p.m.

Verification / Alternative check:
Compute in fractions: 24/9 = 8/3 h = 2 h 40 m, same result.

Why Other Options Are Wrong:
Other times add or subtract incorrect intervals or miscompute initial pages.

Common Pitfalls:
Using total pages typed by A beyond 13:00 by mistake or averaging speeds.

Final Answer:
3:40 p.m.