CAT 2017 Slot 2 — QA Question 2
In a 10 km race, A, B and C, each running at uniform speed, get the gold, silver, and bronze medals, respectively. If A beats B by 1 km and B beats C by 1 km, then by how many metres does A beat C?
Answer & solution
Answer: 1900
In a 10 km race, A beats B by 1 km. So in the time A completes 10 km, B completes
9 km. Therefore ratio of their speeds is 10 : 9.
In a similar way, ratio of speeds of B and C is also 10 : 9
A : B : C
10 : 9
10 : 9
100 : 90 : 81
To get a common ratio for speeds of A, B, C we take LCM of 9 and 10 which is equal to 90 (âµ B is common to both ratios) and equate corresponding values of A and C is also taking B as 90
So if A runs 100m, C runs 81m.
So in a 10 km race, when A runs 10000 m C will run = 8100 m
∴ A will beat C by 10000 - 8100 or 1900 m.
Hence, 1900.