At 5.00 p.m., a black car and a green car left the office and travelled at average speeds in opposite directions round a 40-km route. The black car took 20 minutes to complete each round while the green car took 40 minutes.
- Find the speed of the black car.
- Find the speed of the green car.
- If the two cars travelled without any interval of rest, at what time would the two cars next meet again at the office?
(a)
60 min = 1 h
20 min =
2060 =
13 h
40 min =
4060 =
23 h
Speed of the black car
= 40 ÷
13= 40 x
31= 120 km/h
(b)
Speed of the green car
= 40 ÷
23= 40 x
32= 60 km/h
(c)
LCM of 20 and 40 = 40
40 min after 5 p.m. = 5.40 p.m.
Time that the two cars would meet again at the office = 5.40 p.m.
Answer(s): (a) 120 km/h; (b) 60 km/h; (c) 5.40 p.m.