Area-speed geometry changes while the same flow is conserved. Exact arithmetic here means exact results for the stated model inputs; measured inputs still carry uncertainty and significant-figure limits.
highlighted = computed this step
Wide inlet and half-width outlet close
Inlet area 6 times speed 2 and outlet area 3 times speed 4 both close to flow 12.
6×2=123×4=12
Halving area doubles the needed speed
Inlet area 4 times speed 3 and outlet area 2 times speed 6 both close to flow 12.
4×3=122×6=12
Narrow outlet needs the largest speed
Inlet area 3 times speed 4 and outlet area 1 times speed 12 both close to flow 12.