A car travels from P to Q at a constant speed. If its speed were increased by 10 km/h, it woul have been taken one hour lesser to cover the distance. It would have taken further 45 minutes lesser if the speed was further increased by 10km/h. The distance between the two cities is

Options

A. 540 किमी.
B. 420 किमी.
C. 600 किमी.
D. 620 किमी.

Answer

B

Explanation

माना कि प्रारंभिक गति `xkm//hr` थी तथा दूरी d km है।
`therefore d = (x(x + 10))/((x + 10 - x)) xx 60/60`
`implies d = (x(x + 10))/(10) " "....(i)`
तथा
`d = ((x + 10)(x + 20))/((x + 20 - x - 10)) xx 45/60`
`implies d = ((x + 10)(x + 20))/(10) xx 3/4 " " .....(ii)`
समी. (i) एवं समी. (ii) सेः
`= (x(x + 10))/(10) = ((x + 10)(x + 20))/(10) xx 3/4`
`implies 4x = 3x + 60`
`implies x = 60`
कुल दूरी `(d) = (60(60 + 10))/(10) xx 60/60 = 420km`