Let D’s efficiency be x. Then, C’s efficiency is 1.5x. Together, their combined efficiency is x + 1.5x = 2.5x. Now, total work = 2.5x × 12 = 30x. D’s time to complete the work alone = total work ÷ D's efficiency = 30x ÷ x = 30 days. Final Answer: (b) 30 days
Two trains of same length are running in parallel tracks in the same direction with speed 84 km/hr and 120 km/hr respectively. The latter completely cro...
Train P travelling at 42 km/hr crosses another train Q, having three fourth of its length and travelling in opposite direction at 30 km/hr in 21 seconds...
A train 275 metre long takes 33 sec to cross a man running at a speed of 5 km/hr in the direction same to that of train. What is the speed of the train?
A train can cross a pole in 36 seconds. While if the train increased its speed by 50% then time taken by it to cross 324 metres long platform is 42 seco...
Two cars start from a place with a speed of 45 km/hr at an interval of 10 minutes. What is the speed of a man coming from the opposite direction towards...
A train 270 metre long takes 36 sec to cross a man running at a speed of 4 km/hr in the direction opposite to that of train. What is the speed of the tr...
Two trains, each 150 meters long, are running in opposite directions. If the speed of one train is twice that of the other and they take 20 seconds to c...
A train passes 150 m long platform in 10 seconds and a man standing on the platform in 8 seconds. Find the speed of the train?
Two trains of equal lengths take 20 seconds and 30 seconds respectively to cross a telegraph post. If the length of each train be 300 metres, in what ti...
A train can cross a pole in 32 seconds. While if the train increased its speed by 45% then time taken by it to cross 289 metres long platform is 42 seco...
