Typist A can type a report in 16 hours. Typist B can type the same report in 20 hours and the typist C in 24 hours. All the three typist started typing at 9.00 a.m. at 1.00 p.m. the typist A stopped typing. The other two typists finished the job. Approximately at what time the report was typed?

Work of (A + B + C) for 1 hour = 1/16 + 1/20 + 1/24 = 37/240
∴ Work of (A + B + C) for 4 hours = 4 x 37/240 = 37/60
∴ Remaining work = 1 - 37/60 = 23/60
∴ Work of (B + C) for 1 hour = 1/20 + 1/24 = 11/120
∵ 11/120 work is done by (B + C) in 1 hour
∴ 23/60 work is done by (B + C) = 120/11 x 23/60 = 46/11 hours = 4 hours 11 min.
∴ The type at which the report was typed = 01 : 00 + 04 : 11 = 05 : 11 p.m.