Question

Five light bulbs that are either on or off are lined up in a row. A certain code uses different combinations of lights turned on to represent
different words. If exactly 2 lights must be turned on to represent a word, how many different words can be formed using the 5 light
bulbs? (1 point)

Answer 1

Answer:

10

Step-by-step explanation:

The number of different ways that 2 lights can be chosen from 5 is ₅C₂.  Use a calculator or find the value manually:

₅C₂ = 5! / (2! (5−2)!)

₅C₂ = 5! / (2! 3!)

₅C₂ = 5×4×3×2×1 / (2×1 × 3×2×1)

₅C₂ = 5×4 / 2

₅C₂ = 10