Daniel is taking part in a team building day with his work colleagues.
50 people are attending the activity day.
40 people took part in walking.
18 people took part in sailing.
3 people did neither activity!
One of the people who walked is chosen at random.
Find the probability that this person also sailed.
Answer:
If 3 people did neither activity, then 47 people did either walking and/ or sailing.
Let:
W = people who only walked
S = people who only sailed
X = people who sailed and walked
W + X = 40 (eq 1)
S + X = 18 (eq 2)
W + X + S = 47 (eq 3)
W + S + 2X = 58 (add eq 1 and 2)
W + S = 58 – 2X
Sub back into eq3:
58 – 2X + X = 47
X = 11
So probability that the person also sailed = 11/40