SOLUTION: Question 1: Dino traveled 1.5 hours at 80 km/h for the first 2/5 of his journey. His average speed for the entire journey was 75 km/h. How long did he take to complete the remain

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Question 1115491: Question 1:
Dino traveled 1.5 hours at 80 km/h for the first 2/5 of his journey. His average speed for the entire journey was 75 km/h. How long did he take to complete the remaining part of the journey.
Question 2:
Betty was driving from Rock City to Stone City. She had covered 2/7 of the journey when she passed Barney who was driving at an average speed of 60 km/h. 2.5 hours after passing Barney along the same road, Betty reached Stone City while Barney was still 30 km away from Stone City.If Barney was also driving from Rock city to Stone City, How long did he take to cover the distance between two places.
Answer by ankor@dixie-net.com(22740) About Me  (Show Source):
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Dino traveled 1.5 hours at 80 km/h for the first 2/5 of his journey.
His average speed for the entire journey was 75 km/h.
How long did he take to complete the remaining part of the journey.
:
Find the distance traveled in 1.5 hrs at 80 km/hr
1.5*80 = 120 km
let d = the total distance of the journey (2%2F5d = .4)
.4d = 120
d = 120%2F.4
d = 300 km is the total distance
:
let t = time traveling the remainder of the journey
1.5 + t = 300%2F75
1.5 + t = 4 hrs
t = 4 - 1.5
t = 2.5 hrs
:
:
Question 2:
Betty was driving from Rock City to Stone City.
She had covered 2/7 of the journey when she passed Barney who was driving at an average speed of 60 km/h.
2.5 hours after passing Barney along the same road, Betty reached Stone City while Barney was still 30 km away from Stone City.
If Barney was also driving from Rock city to Stone City,
How long did he take to cover the distance between two places.
:
Find the distance from Rock C to Stone C
let d = dist between the two towns
Bet covered 5%2F7d in 2.5 hrs, while
Barn covered (5%2F7d - 30) in that time
%28%285%2F7%29d+-+30%29%2F60 = 2.5
5%2F7d - 30 = 60 * 2.5
5%2F7d = 150 + 30
5%2F7d = 180
d = 7%2F5*180
d = 252 mi is the distance between the cities
therefore
252%2F60 = 4.2 hrs for Barn to cover the distance between the cities
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