Nina, Shanti and Belle run a 1000 m race at a constant speed. When Nina crossed the finish line first, she was 200 m ahead of Shanti and 400 m ahead of Belle. When Shanti crossed the finish line, how far ahead of Belle was she?

The correct answer is: 250 m

Let the constant speeds of Nina, Shanti and Belle be x, y and z.
Step 1 of 2:
When Nina crossed the finish line, the Distance travelled by Shanti is (1000 - 200 =)800 m and the Distance travelled by Belle is (1000-400 = )600 m.
Time taken by Nina to cross finish line = Time taken by Shanti to travel 800 m

……(1)
Time taken by Nina to cross finish line = Time taken by Belle to travel 600 m

 ……(2)
From equations (1) and (2)

  ……(3)
Step 2 of 2:
Time taken by Shanti to travel the remaining 200 m = 
Distance travelled by Belle  in  time = Speed × Time = z × 
So, when Shanti crossed the finish line, position of belle = 600 + 
Gap between Shanti and Belle = Final position of Shanti - Final position of Belle
= 1000 - (600 + )
From equation (3), put y = 
Gap between Shanti and Belle = 1000 - 600 -  = 400 - 150 = 250 m
Final Answer:
Hence, when Shanti crossed the finish line, Shanti was 250 m ahead of Belle.