If this is the question I'm thinking it is... then....
The part swimming and cycling = 1/4 + 3/5
= 17/20
The part remaining after swimming and cycling
= 1/1 – 17/20
= 17/17 – 17/20
= 3/20
if 3/20 part = 3600
then 1 full part = 3600 × 20/3 = 24000
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