# Multiple Choice - Answers (1 Viewer)

##### New Member
how is the anwser to question 19 A?
wouldn't it be 10% if it went foward by 20 then back by ten. ie. 20 -10 =10%??

#### stressed02

##### Member
i got 10% as well... but then again i suck

#### SparklingDimond

##### Member
If the population is 100, then it increases by 20 so then it's 120.

The next yr it decreases by 10% of 120, ie. 12, so the then it's 108

Therefore the population has increased by 8%

#### stressed02

##### Member
ohhh yes that makes sense now

#### SparklingDimond

##### Member
For 18 I can't remember if I got b or c, but my working is different.
P(first prize) is 1/200
P(second prize) is also 1/200? because she only bought one ticket and we're not trying to work out her chances of getting first AND second prize? well that's what i think anyway.

sooo working is: \$100 X 1/200 + \$50 X 1/200 - \$1 (cause that's how much she payed for the ticket) = -\$0.25 (C)

#### Lazarus

##### Retired
Oh yeah. She had to pay \$1 for the ticket.

I think I'm going to stop trying to answer general maths questions.

The second probability is still 1/199, SparklingDiamond, because when she doesn't win the first prize, someone else must win it instead, and so their ticket will be 'used up'.

True dat laz....

#### nomza

##### Member
Hey, does the probability go down with the ticket drawn???
like \$100 x 1/200 (+) 50 x 1/199 etc ????

I dunno, I don't remember my working...

#### Lazarus

##### Retired
Yes, the probability will decrease.

After the first prize is won, there will be one less ticket in the total ticket 'pool', as it was used to win that prize. And so the winning ticket for the second prize is drawn from a pool of 199 tickets, not 200.

#### SparklingDimond

##### Member
But--isn't it still 1/200 cause of the 200 tickets that were sold, one of them is going to get second prize? Otherwise the chance of coming last (hypothetically; if there were prizes for every place) would be 1/1. I'm confusing myself...any thoughts?

#### Lazarus

##### Retired
You are correct that, of the 200 tickets sold, one of them is going to get second prize.

However, the second prize will be drawn after the first prize is drawn (that's why it's the 'second' prize). At this stage, there are only 199 tickets left to choose from.

If there were 200 prizes, after the first 199 prizes are given away, the probability of winning the 200th prize is 1, yes.

#### SparklingDimond

##### Member
Bugger
Any answers for any of the other questions yet?

#### Lazarus

##### Retired
Slowly going through them... I'm reluctant to do them, because I don't know the actual methods you guys have been taught. and I occasionally have to look something up myself, not having done it before. which is annoying.

#### The Spruce Moose

##### Member
these anwsers are a total screw up

#### WaTs 2 CuM AhEd

##### Member
hmmmmmmm i know where im heading now then