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Points A and B are 70 km apart on a highway. A car starts from A and another car starts from B at the same time. If they travel in the same direction, they meet in 7 hours, but if they travel towards each other they meet in one hour. What are their speeds in km/hr?

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One of the most important and conceptual question from linear equations in two variables in which we have to calculate the speed of two cars if they are at a distance of 70 km and if they travel in same distance try meet in 7 hrs and they travel in opposite directions they meet in 1 hr.

Kindly give me a detailed solution of this question

RS Aggarwal, Class 10, chapter 3E, question no 31


1 Answer

  1. Let car speed from point A=xkm/hr.
    and car speed from point B=ykm/hr.

    Distance = speed × time
     Distance from A=x×7=7x
    Distance from B=y×7=7y
    If they travel in the same direction, they meet in 7 hours. Point A and B are 70km apart.
    xy=10         …(i)

    if they travel towards each other they meet in one hour. Point A and B are 70km apart.
    x+y=70             …(ii)

    Adding (i) and (ii). we get

    substituting x=40 in (i). we get
    x=40km/hr  and y=30km/hr.

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