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A train travels at a certain average speed for a distance of 63 km and then travels at adistance of 72 km at an average speed of 6 km/hr more than its original speed. If it takes 3 hours to complete total journey, what is the original average speed ? |
Answer» ☆ Solution ☆Given :-
To Find :-
Step-by-Step-Explaination :-Let the original speed be x As we KNOW that :- Distance = Speed × Time Speed = Distance / Time Time = Distance / Speed We have, Distance travels = 63 km Next distance travelled = 72 km Speed = ( x + 6 ) km/ h Time = 72/ ( x + 6 ) hrs 63 / x + 72 / x + 6 = 3 Total journey completed in 3 hour. According to the QUESTION, => 63 / x + 72 / ( x + 6 ) = 3 => 63 ( x + 6 ) + 72x = 3x ( x + 6 ) => 21 ( x + 6 ) + 24x = x ( x + 6 ) => 45X + 21 × 6 = x^2 + 6x => x^2 - 39x - 126 = 0 => x^2 - 42x + 3x - 126 = 0 => x ( x - 42 ) + 3 ( x - 42 ) = 0 => ( x - 42 ) ( x + 3 ) = 0 => x = 42 and - 3 Hence,42 km/hr is the original average speed. |
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