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
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.
⇒7x−7y=70
⇒x−y=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
2x=80
∴x=40
substituting x=40 in (i). we get
40−y=10
∴y=30
∴x=40km/hr and y=30km/hr.