2009 CFAI Q9: The duration of the fixed leg is 75% of its maturity. Is this convention?
No but some questions specify that. Makes calculating the duration really easy.
Fixed 0.75(Maturity)
Floating 0.50(Payment frequency e.g 0.25 for quarter)
Swap duration from fixed receiver perspective f.ex. +Duration Fixed - Duration Floater. Almost always longer duration.
This is approximation but works on CFA as well as on FRM exam.
Only for the exam. In the real world you just use computers to estimate the duration of each leg and take the difference.