Answer:
11 hurdles
Step-by-step explanation:
First hurdle = 45 m from start
Last hurdle = 40 m from finish
Other hurdles = 35 m apart
Let h = number of hurdles 35 m apart
400 = 45 + 40 + 35h
400 = 85 + 35h
400 - 85 = 35h
315 = 35h
h = 315 / 35
h = 9
Total number of hurdles = First hurdle + Last hurdle + Other hurdles
= 1 + 1 + 9
= 11 hurdles
Total number of hurdles = 11