Speed P6

Mary and Ken travelled from Town A to Town B. Mary left Town A at 0915 and took 4 h to reach Town B. Ken left Town A at 1000 and took 2 h 45 min to reach Town B. At what time did Ken pass Mary?

  9.15 am.
M  [      DM              ][                ] D
                           4 DM/D          4 h
                            
   10 am
K  [       DM           ][                   ] D
                       2 3/4 DM/D       2 3/4 h

9 1/4 + 4 DM/D --> 10 + 2 3/4 DM/D

(4 - 2 3/4) DM/D --> 10 - 9 1/4 = 3/4

DM/D --> 3/4 x 4/5 = 3/5

3/5 x 4 = 2 2/5 h
           = 2 h 24 min

           2 h               24 min
|------------------|-------------|
9.15 am      11.15 am      11.39 am


or

3/5 x 2 3/4 = 1 13/20 h
                  = 1 h 39 min

              1 h             39 min
|-------------------|-------------|
10 am             11 am       11.39 am

Ken passed Mary at 11.39 a.m.