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places a&b are 80 km away from each other.a car starts from A and another from B.if they move i n same direction. they meet in 8 horrs.if they move in opposite direction they meet in 1 hour20 min.find their speed |
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Answer» Let the speed of the first car which starts from A = x km /hr Speed of the second car which starts from B = y km / hr We know that,______________________Time = distance / speed______________________ Distance between two places A and B are 80km d = 80 km i ) if the cars move in same direction Relative speed of them = ( x + y ) km/hr Time = 8hr d = 80km 8 = 80 / ( x + y ) x + y = 80 / 8 x + y = 10 ------( 1 ) ii ) if two cars moving opposite direction, Relative speed = ( x - y ) km / hr Time = 1 hr 20 minutes = ( 1 + 20 / 60 ) hr = ( 80/60) = 4/3 hr d = 80km 4/3 = 80 / ( x -y ) x -y = ( 80 × 3 ) / 4 x - y = 60-----( 2 ) Add ( 1 ) and ( 2 ) , we get 2x = 70 x = 35 Put x = 35 in ( 1 ) we get , y = 25 Therefore , Speed of the first car = x = 35km/hr Speed of the second car = 25km /hr |
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