Ms Li works at an office
where the work timing is from 9:00 AM to 6:00 PM. 25% of a year she goes late
to office and 35% of a year she leaves early from office. If P is the
probability that she works at office the entire day then
(a) 0.25 <= P
<= 0.35
(b) 0.25 <= P
<= 0.65
(c) 0.4 <= P
<= 0.65
(d) 0.35 <= P
<= 0.4
Answer: (c)
Explanation:
The minimum value for the
probability P is obtained by considering that on none of the days when she went
late to office did she leave early from office. This means that (25% + 35%) =
60% of the days she either went late to office or left early from office i.e., 60% of the days she did not work the entire
day. Hence 40% of the days she could have worked the entire day.
Next, to establish the
maximum value for the probability P, consider that 25% of the days when she
went late to office falls under the 35% of days when she left early from
office. Hence 35% of the days she would have either gone late of left early
from office. Hence, 65% of the days she could have worked the entire day.