Answer:
the expected distance is 4.32 m
Step-by-step explanation:
given data 
half life time = 1.8 × 
 s
 s
speed = 0.8 c = 0.8 × 3 × 
 
 
to find out
expected distance over 
solution
we know c is speed of light in air is 3 × 
 m/s
 m/s
we calculate expected distance by given formula that is
expected distance = half life time × speed .........1
put here all these value 
expected distance = half life time × speed 
expected distance = 1.8 × 
 × 0.8 × 3 ×
 × 0.8 × 3 × 
 
 
expected distance = 4.32
so the expected distance is 4.32 m