All Leaving Cert Mathematics posts
• #### Maths Question MrDarcyAndMe

Could somebody please answer this question for me? I'm getting a different answer to what the back of the book says...

Q. Of 70 people surveyed, 35 were members of a soccer club, 50 were members of a rugby club and 3 were not members of either of the two clubs.

What is the probability that a person picked at random is a member of at least one club?

I just took the 3 people who weren't part of any club away from the total number being surveyed and got 67/70, which makes sense to me because that's how many people are in the two clubs. But apparently I'm wrong? Or maybe there's a typo in the back of the book...

1. #### NDoonan

you are correct because the probability of at least one club means the probability of 1 club, 2 clubs etc... so its 67/70

another way of looking at the question is to find out whats the probability that a person is a member of NO clubs. The answer would be 3/70. so that would mean that the probability of at least one club is [1- (probability that a person is a member of NO club)]= 1-3/70= 67/70.

never trust answers in book as they are not always 100% accurate

2. #### michael.ryan.712714

Trust yourself mate. Self belief is the key to success in mathematics

3. #### MrDarcyAndMe

NDoonan and michael.ryan.712714 Thanks a MILLION both of you!

No problem