John took half an hour to row 3 km with the current. When he returned, he took 90 min. Find his rowing rate and speed of the current. This is my solving (but wrong . Eq1+1/3(Eq2) 3=30r+30t 1=30r-30t ----------- 4=60r r=4/60 and then you substitute r in any of the equations to find t, but r is supposed to be 4 O.o

Question

John took half an hour to row 3 km with the current. When he returned, he took 90 min. Find his rowing rate and speed of the current.

This is my solving (but wrong >.< ):

3=30r+30t
3=90r-90t

=> Eq1+1/3(Eq2)
     
3=30r+30t
1=30r-30t
-----------
4=60r
r=4/60 and then you substitute r in any of the equations to find t, but r is supposed to be 4 O.o

apoorvk · Answer

Your work seems alright to me, @aroub . There seems to be a problem with the given answer. Could that be a printing error or something?

aroub · Answer

I really don't think so.. Because my teacher AND the book answered it r=4 and t=2

experimentx · Answer

Multiply it by 60 ... get you answer is 4 km/hr
that's all right

experimentx · Answer

what you are getting is 4/60 km/min

apoorvk · Answer

oh yeah - the units!!
*facepalm*

aroub · Answer

Aooh! Right! I totally forgot about that :P Thank youu =D