easy · GMAT Quant
A traffic light system runs a 4-step signaling test using signals Red (R), Yellow (Y), and Green (G). No two adjacent steps can display the same signal, and signal Yellow (Y) cannot appear in position 1 or position 3.
How many valid 4-step test sequences can be performed?
- 8
- 10
- 12
- 16
- 20
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