Question 809854
Bob is climbing down a ladder while Roy is climbing up another one.  Each ladder has 30 rungs.  Bob went down 2 rungs every second while Roy went up 1 rung every second.  At some point they were at the same height.  Which rung were they on?

 Bob went down 2 rungs every second
 while Roy went up 1 rung every second.

they are moving towards each other add up their rates

2+1=3 rungs/second

total 30 rungs

time taken to meet is d/r
30/3
=10 seconds

bob rate = 2 rungs/s . d=rt, 2*10= 20 rungs from top