Maths is scary! Help!

[misskatie90]

Hey this is a long shot.
Am doing a level 5 in social care and I need my maths qualification.
I am at a stand still with a question can anyone help.

In a survey of 200 people on transportation methods, 52 stated they drove, 82 stated they took the train, and 19 stated they walked. What is the proballity that a person selected at random would walk? Give your answer to three decimal places.

Any help would be great

19 out of 200 people walked.
19/200 = 0.095

Ignore me - I've misse a bit!

Or have I? Not everyone answered. 🤔

I think it's still right.

I can't help because I'm not very good at maths, but can I recommend Hegarty Maths? Google hegarty maths probability and videos of him explaining it will come up. Sorry I can't make link work.

Does it say what the rest of the 200 did?

I'm going to assume the remainder of the 200 who didnt give an answer dont walk.

So.

Imagine all 200 of them in a big sack. You reach in and grab one. Your chance of grabbing:-
A driver - 52 out of 200
A Walker - 19 out of 200
A trainer - 82 out of 200
Someone who does none of the above- 47 out of 200

To answer the walk part - 19 out of 200 = 19 ÷ 200.

It’s 19 out of 200 who walked, so posters saying it’s 19/200 are right. The answer is 0.095.

It’s a bit odd that they don’t add up to 200 and also that the answer is already to 3dp.

Thank you everyone so helpful.

What about if it's in fraction format.. here's another question. I just need to get my head around it.

Sergei has a 3/5 chance of getting his questions correct.
Alex has a 3/4 chance of getting her questions correct.

What is the probalility of Sergei getting his next two questions correct?

Thank you in advance

What is the probalility of Sergei getting his next two questions correct?

That depends if Sergei has revised!

If you’re looking for the probability something happening AND something else happening you multiply the probabilities together.
3/5 x 3/5 = 9/25

Probability shown as 3/5 is the same as 3 ÷ 5.

He has a 3 in 5 chance of getting his questions correct. Whether that's 1 question or 100 questions.

So the answer is 3 in 5.

@BernadetteRostankowskiWolowitz

Probability shown as 3/5 is the same as 3 ÷ 5.

He has a 3 in 5 chance of getting his questions correct. Whether that's 1 question or 100 questions.

So the answer is 3 in 5.

This is not correct. That would be the probability of him getting any individual question correct. The question is asking for the probability of getting question 1 AND question 2 correct. BOTH questions need to be right. That’s why you need to multiply the probabilities together.

Try thinking of it in terms of coins. The probability of getting a head (H) is 0.5 or 1/2
The probability of getting a tail (T) is also 1/2.

The four options for tossing a coin twice are
HH
HT
TH
TT

The probability of getting a head is still 1/2 on every throw, but the probability of getting two heads is only 1/4. That’s because you need a H on throw one AND on throw 2.

1/2 x 1/2 = 1/4 or 0.25 or 25%

I hope that makes it clearer!

Ah of course.

I feel like am getting somewhere and then they ask me a question which I know is similar but worded differently.
Can someone explain this one please.

Angela has 4 hat styles, each style is available in 4 colours : red, black, white, green. If she randomly selects 4 hats, 2 from each style, what is the probability that she will choose red hats? Give your answer as a fraction.

My heads going to explode

Maybe it's easier to think of there being a hundred Sergeis who all have to answer the two questions. We know that on the first question, 3 out of 5 Sergeis will get it right, so 60 out of 100 Sergeis. The other 40 Sergeis got it wrong, so we can ignore them because they now can't get both of the answers right. Then the 60 Sergeis who got the first question right do the second question. 3 out of 5 of them get it right, which is 36 Sergeis.

So 36 out of our original 100 Sergeis will get two right answers — 36/100, 0.36, 36%, or 9/25.

At which point the person you're caring for goes "why the fuck are you giving me four random hats".

Start by working out the probability of getting a red hat from style 1. There are four colours, only one red so the probability of red is 1/4.
Then look at style two. Again, four colours, one red so the probability of getting a red is 1/4.

Now you need the probability of getting red style 1 AND red style 2.
Multiply those probabilities together.
1/4 x 1/4 = 1/16 chance of getting two red hats.

2 from each style is 8 hats..?

She can't select 2 from each style, giving her 4 hats. 4 x 2 = 8.

That's a poorly-worded question.

Sorry I’ve totally misread that question.

Probability of getting a red hat from each style is 1/4
Probability of getting two red hats from each style is 1/4 x 1/4 = 1/16

You need that to happen four times to allow for two red hats from each style.
1/16 x 1/16 x 1/16 x 1/16 = 1/65536

Or if you’re happy with powers, you need an event with a probability of 1/4 to happen eight times. That’s 1/4^8

@thecatfromjapan

She can't select 2 from each style, giving her 4 hats. 4 x 2 = 8.

That's a poorly-worded question.

I agree, it should say the hat is replaced after each pick.

I think part of your problem is that these questions aren't good.

Eg. Your second question, I read that as Sergei answering three questions in total, not two.

Plus, practice questions should have numbers that make visible the process they're trying to reinforce, iyswim. And your first question didn't do that.

Is this course-material you're working from? Or could you find a good maths practice book to look at?

Eg. Your second question, I read that as Sergei answering three questions in total, not two.

I think that one’s ok. It’s the NEXT TWO questions correctly. That’s clearly the probability of getting two questions in a row correct.

I totally agree that the hat one is very poorly worded.

@FrankensteinIsTheMonster

Maybe it's easier to think of there being a hundred Sergeis who all have to answer the two questions. We know that on the first question, 3 out of 5 Sergeis will get it right, so 60 out of 100 Sergeis. The other 40 Sergeis got it wrong, so we can ignore them because they now can't get both of the answers right. Then the 60 Sergeis who got the first question right do the second question. 3 out of 5 of them get it right, which is 36 Sergeis.

So 36 out of our original 100 Sergeis will get two right answers — 36/100, 0.36, 36%, or 9/25.

To find a fraction of something, you multiply the thing by the fraction, right? — for example, if you want to find out what three quarters of a number is, you multiply your original number by ¾ (which is the same as 3÷4, which is 0.75). So to find ¾ of 200, you would multiply 200 by 0.75 and get 150.

When you're being asked the probability of two things both happening, you're being asked for a fraction of a fraction, because only some of the Sergeis will get one of the questions right, and out of those who do, only some of them will also get the other question right. So you're trying to work out the size of a subset of a subset of the Sergeis — in this case three fifths of three fifths. To find 3/5 of 3/5, you can multiply them together by multiplying the top numbers with each other and the bottom numbers with each other — 3x3 is 9, 5x5 is 25, so the answer is 9/25.

But it actually all gets really complicated and horrible with probability depending on exactly how the question is worded, and then you get shit like the Monty Hall problem, which, just don't.