show all work as you solve the following problems and write

show all work as you solve the following problems and write complete answers, including appropraite units

mark left Pranav\'s house and traveled toward his friend\'s house. One hour later Stefan left traveling 10 km/h faster in an effort to catch up to him. After three hours Stefan finally caught up. What was Mark\'s average speed?

Solution

Let mark\'s average speed, be S Then stefan\'s is: S + 10 Time taken for stefan to get to catch-up point: 3 hours Time taken for mark to get to catch-up point: 3 (3 + 1) hours When stefan catches up to mark, both would\'ve travelled the same distance, and so, we get: 3S = 2(S + 10) 3S = 2S + 20 3S - 2S = 20 S, or mark\'s speed = 20 kmph