Question 350854: Dear sir,
Please help me with the following questions. I have solved one of them for which i wanted to know whether the logic used is correct or not. Is there any other way of solving it.
hope u will send the solutions at the earliest. Thank you.
1. An earthworm of length 15cm is crawling along at 2cm/s. An ant overtakes the worm in 5 seconds. How fast is the ant walking?
Ans. The speed of the ant is 15/5 =3 cm/s.
The earthworm is moving at the speed of 2 cm/s. Therefore, the speed of the ant will be 3 plus 2 = 5cm/s.
2. A car completes a journey at an average speed of 40km/h. At what speed must it travel on the return journey if the average speed for the complete journey (out and back) is 60km/hr?
Answer by Alan3354(69443)   (Show Source):
You can put this solution on YOUR website! 1. An earthworm of length 15cm is crawling along at 2cm/s. An ant overtakes the worm in 5 seconds. How fast is the ant walking?
Ans. The speed of the ant is 15/5 =3 cm/s.
The earthworm is moving at the speed of 2 cm/s. Therefore, the speed of the ant will be 3 plus 2 = 5cm/s.
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That's reasonable, but there's no info on how far away the worm was when the ant started.
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2. A car completes a journey at an average speed of 40km/h. At what speed must it travel on the return journey if the average speed for the complete journey (out and back) is 60km/hr?
d = the distance
t = time
r = rate
r (going) = 40
t = d/40
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Round trip:
t = d/40 + d/r = 2d/60
d/40 + d/r = d/30
Multiply by 120r
3dr + 120d = 4dr
dr = 120d
r = 120 km/hr
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