A car covers a distance of 360 km at a uniform speed. If the speed had been 15 km/h more, it would have taken 2 hours less for the journey. Find the original speed of the car. MCQ with Answer and Explanation
A car covers a distance of 360 km at a uniform speed. If the speed had been 15 km/h more, it would have taken 2 hours less for the journey. Find the original speed of the car.
A. 45 km/h
B. 50 km/h
C. 55 km/h
D. 60 km/h
Answer: Option A
Solution (By JKSSB Mock Tests)
Let original speed be s. 360/s - 360/(s+15) = 2 => 180/s - 180/(s+15) = 1 => 180(15) = s(s+15) => 2700 = s(s+15). Solving s^2 + 15s - 2700 = 0 gives (s - 45)(s + 60) = 0. Since speed is positive, s = 45 km/h.
Two cars leave a location simultaneously at a right angle to each other. Their speeds are 36 km/h and 48 km/h respectively. Find the direct distance between them after 15 minutes.
Explanation:
Time = 15 minutes = 0.25 hours. Distance covered by first car = 36 * 0.25 = 9 km. Distance covered by second car = 48 * 0.25 = 12 km. Since they travel at right angles, distance between them = sqrt(9^2 + 12^2) = sqrt(81 + 144) = sqrt(225) = 15 km.
Explanation:
Let stream speed be c. Upstream speed = 15 - c, Downstream speed = 15 + c. Given: 2 * (15 - c) = 15 + c => 30 - 2c = 15 + c => 3c = 15 => c = 5 km/h.
No comments yet. Be the first to start the discussion!