self Maths Puzzle

Calvin went cycling in San Francisco, which is extremely hilly. He can pedal up a hill at a speed of 12 mph, and down a hill at a speed of 36 mph. If he went up and down a hill (back to the same point), what is his average speed (in mph) for the entire journey?

Read Solution (Total 3)

18mph
average speed= (2*up speed*down speed)/(up speed +down speed)
so, (2*12*36)/(12+36)=18mph
11 years agoHelpfull: Yes(3) No(0)

average speed is..(2*12*36)/(12+36)=18mph
11 years agoHelpfull: Yes(1) No(0)
average speed=(2*12*36)/(12+36)
=18mph Ans.
11 years agoHelpfull: Yes(1) No(0)

self Other Question

Jack and Danny are bricklayers. Jack can build a certain brick wall in 8 hours whereas Danny takes 11 hours. If they work together, their combined rate decreases by 7 bricks an hour, and it only takes them 5 hours to build the wall together. Find the number of bricks in the wall Excluding stoppages,the speed of the bus is 54kmph and including stoppages,it is 45kmph.for how many min does the bus stop per hr.