hi everyone
one robot builds a robot in 1 hr' and another one builds a robot in 2 hr. the 2 robots work together, and when a new robot is complete, it joins the others, working at a constant rate of 1 robot in 2 hr, how much time will it take untill there are 5 robots altogether, if the robots build only one robot a time?
1-70 min
2- 94 min
3- 110 min
4- 112 min
5- 120 min
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