The statements in the question can be reformulated as follows: If A covers 400m, B covers 395m. If B covers 400m, C covers 396m. If D covers 400m,C covers 384m. Therefore, if B covers 395m,then C will cover,
396
400
×395=391.05m Again, If C covers 391.05m, then D will cover
400
384
×391.05=407.34m Thus, if A and D run over 400m, then D wins by 7.3m.