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If we pick at least 5 red balls, 6 green balls and 8 blue balls from the box, the total number of balls picked from the box will be 19. If one more ball is picked from the box, irrespective of what it is, it can be said that at least 6 red balls or at least 7 green balls or at least 9 blue balls have been picked from the basket. Hence, required number of balls = 19 + 1 = 20
A train moves at 90 km/h and needs to cover a journey in 2 hours. It halts for 10 minutes at the midpoint. What speed must it take for the second half?