Answers

2016-05-07T19:09:14+05:30
Here, the total distance to be covered is 40m. above ground level and the 20m below. 
Hence, d = (40 + 20) m.
               = 60 m.
We know that: speed = 3 m. /min.
We also know that: s= \frac{d}{t} \\  \\ t=  \frac{d}{s} \\  \\ t= \frac{60}{3}    \\  \\ t=20min
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The Brainliest Answer!
2016-05-07T19:48:48+05:30
Speed=distance/time
we need time
time=distance/speed
Distance is 40 above ground+20 below gound=60m.(total)
Speed is 3m/min
substitute in formula
t=60/3
t=20min
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