this is the tunnel problem right? I have the 2010 edition but I believe the questions are not reshuffled or even corrected.
the answer is wrong.
the two crews combined rate is 30 feet per day. in order to dig 300 feet it would take 10 days to complete. 30ft per day X 10 days = 300 feet.
after 10 days crew A would only dug 120 feet. crew B would have dug 180 feet.
120feet + 180 feet = 300 feet. they've completed digging the tunnel.
