The Student Room Group
Competition - post a photo you've taken of nature >>
Competition - post a photo you've taken of nature >>
Competition - post a photo you've taken of nature >>

Maths

I need help with this question:
20) There are only red sweets and yellow sweets in a bag.
There are n red sweets in the bag.
There are 8 yellow sweets in the bag.
Sajid is going to take at random a sweet from the bag and eat it.
He says that the probability that the sweet will be red is
7/10(a) Show why the probability cannot be
7/10
Original post by raidas0001
I need help with this question:
20) There are only red sweets and yellow sweets in a bag.
There are n red sweets in the bag.
There are 8 yellow sweets in the bag.
Sajid is going to take at random a sweet from the bag and eat it.
He says that the probability that the sweet will be red is
7/10(a) Show why the probability cannot be
7/10

2/10 ,because 8/10 + 2/10 = 10/10 ,since the 10 in the denominator reveals the number of candies in the bag as a whole
although this question involves sweets, it should not really be in the Food and Drink forum

:hmmmm2:
Original post by raidas0001
I need help with this question:
20) There are only red sweets and yellow sweets in a bag.
There are n red sweets in the bag.
There are 8 yellow sweets in the bag.
Sajid is going to take at random a sweet from the bag and eat it.
He says that the probability that the sweet will be red is
7/10(a) Show why the probability cannot be
7/10

What are your thoughts?
I thought under 13s weren't allowed on TSR? :confused:
Original post by lucydales
2/10 ,because 8/10 + 2/10 = 10/10 ,since the 10 in the denominator reveals the number of candies in the bag as a whole

No, that's not correct
Reply 6
Avatar for raidas0001
raidas0001
OP
4
Original post by Muttley79
What are your thoughts?

n/(n+8)=7/10
10n=7n+56
3n=56
n=18.66666666666666
if the probability of getting red is 7/10 then there is a decimal number of red sweets and u can't have 0.6666666667 of a sweet.
i am not sure if i'm correct
Original post by raidas0001
n/(n+8)=7/10
10n=7n+56
3n=56
n=18.66666666666666
if the probability of getting red is 7/10 then there is a decimal number of red sweets and u can't have 0.6666666667 of a sweet.
i am not sure if i'm correct


Yep, looks good.

I'd reword it slightly, since in general all numbers are decimal (it just means base 10).

If the probabilty of getting a red is 7/10, then there must be 18 2/3 sweets. Since the number of sweets must be a whole number it follows you can't get a probability of getting a red being 7/10 .
Original post by Muttley79
What are your thoughts?

Leading on from this question:

After Sajid has taken the first sweet from the bag and eaten it, he is going to take at random a second sweet from the bag. Given that the probability that both the sweets he takes will be red is 3/5.

Work out the number of red sweets in the bag.
Original post by raidas0001
I need help with this question:
20) There are only red sweets and yellow sweets in a bag.
There are n red sweets in the bag.
There are 8 yellow sweets in the bag.
Sajid is going to take at random a sweet from the bag and eat it.
He says that the probability that the sweet will be red is
7/10(a) Show why the probability cannot be
7/10

The reason why it can't be 7/10 is that then the number of sweets wouldn't be whole and that does not make sense to have something like half a candy.

If the probability of a red sweet is 7/10 then the probability of a yellow sweet is 3/10 meaning that the number of total sweets will be 8*10/3 which is 26 3/4. This doesn't make sense as mentioned before, non-whole numbers don't make sense.
Original post by raidas0001
I need help with this question:
20) There are only red sweets and yellow sweets in a bag.
There are n red sweets in the bag.
There are 8 yellow sweets in the bag.
Sajid is going to take at random a sweet from the bag and eat it.
He says that the probability that the sweet will be red is
7/10(a) Show why the probability cannot be
7/10

Leading on from this question:

After Sajid has taken the first sweet from the bag and eaten it, he is going to take at random a second sweet from the bag. Given that the probability that both the sweets he takes will be red is 3/5.

Work out the number of red sweets in the bag.
Nope, you need an algebraic explanation for that create a simple expression from teh info given to you and you will realise you just do not get a whol enumber
(edited 3 years ago)
what exam paper is this question from?
Reply 13
Avatar for P05316
P05316
Original post by raidas0001
n/(n+8)=7/10
10n=7n+56
3n=56
n=18.66666666666666
if the probability of getting red is 7/10 then there is a decimal number of red sweets and u can't have 0.6666666667 of a sweet.
i am not sure if i'm correct


yes that is correct

Quick Reply

Related discussions

Latest

Trending

Trending

Articles for you