JayPatadiya
Pankaj started walking from point A to point B and Prakash started walking from point B to point A, both started at 6:00 AM. After walking for 2 hours, both met each other and sat down for breakfast, which took 1 hour. Then both continued their journey. Since they just had their brakfast, their speed reduced to half of their original speed. After one hour, Prakash realized that their keys got exchanged, so he started running towards Pankaj at two and a half times his present speed. If the ratio of Pankaj's and Prakash's original speed was 3:2, at what time would Prakash and Panakj meet to exchange their keys?
A.12:00 PM
B.12:30 PM
C.01:00 PM
D.01:30 PM
E.11:30 AM
6am-8am:
Let Pankaj's rate = 6 miles per hour and Prakash's rate = 4 miles per hour, with the result that their rate ratio = 6:4 = 3:2.
8am-9am:
Breakfast
9am-10am:
Pankaj's rate decreases by 50% to 3 miles per hour.
Prakash's rate decreases by 50% to 2 miles per hour.
When Pankaj and Prakash travel away from each other, they WORK TOGETHER to increase the distance between them.
When people work together, ADD THEIR RATES.
New combined rate for Pankaj and Prakash = 3+2 = 5 miles per hour.
Since their combined rate = 5 miles per hour, the distance between them after 1 hour = r*t = 5*1 = 5 miles.
10am - key exchange:
Prakash's increased rate = 2.5 times his post-breakfast rate of 2 miles per hour = 5 miles per hour.
Since Prakash and Pankaj are separated by 5 miles, Prakash must CATCH UP by 5 miles to perform the key exchange.
The CATCH-UP rate is the DIFFERENCE between Prakash's increased rate and Pankaj's post-breakfast rate:
5-3 = 2 miles per hour.
Since Prakash must catch up by 5 miles at a catch-up rate of 2 miles per hour, the time to catch up \(= \frac{d}{r} = \frac{5}{2} = 2.5\) hours.
Thus:
Time of the key exchange = 10am + 2.5 hours = 12:30pm.