Mathematics Question Thread

[amelia20181]

how do you do this

[fun_jirachi]

how do you do this

I don't know if this is a legit way of doing it, but this is the way my teacher taught me.
So with evaluating limits, you just sub in a small number that is close to the number x is approaching, so for this example, sub in 0.001 or something, and you get 0.2499999583. If you keep subbing in even smaller values, the calculator just spits out a definitive value of 0.25, which is your answer.

[amelia20181]

also this question

[RuiAce]

I don't know if this is a legit way of doing it, but this is the way my teacher taught me.
So with evaluating limits, you just sub in a small number that is close to the number x is approaching, so for this example, sub in 0.001 or something, and you get 0.2499999583. If you keep subbing in even smaller values, the calculator just spits out a definitive value of 0.25, which is your answer.

You can't sadly; that technique more or less exists to help make students' lives easier when graphing things with asymptotes.

That particular question requires the limit \( \lim_{\theta \to 0} \frac{\sin \theta}{\theta} = 1 \) which is a known result. Although you'd sub \(\theta = 4x\) to obtain \( \lim_{x\to 0} \frac{\sin 4x}{4x} = 1\). It's a limit that's taught in the 2U course but never examined in 2U; only in MX1.

[fun_jirachi]

also this question

First one is similar to integrating sin x, but in degrees.

Second one

[amelia20181]

would the answer for this question be 1.88

the ratio of boys to girls in Redwell high school is 3:5. The ratio of boys to girls in Southcourt high school is 2:3. A student is chosen from redwell high school and then another student is chosen from Southcourt high school. Find the probability that at least one girl is chosen.


claudia is one of 10 employees in a company. This month the company will commence holding a charity fundraising raffle at the end of each month. There is only one winner each month. what is the probability that claudia will win the raffle exactly once within the first four months?

for this question would it be 2.8

[fun_jirachi]

would the answer for this question be 1.88

the ratio of boys to girls in Redwell high school is 3:5. The ratio of boys to girls in Southcourt high school is 2:3. A student is chosen from redwell high school and then another student is chosen from Southcourt high school. Find the probability that at least one girl is chosen.


claudia is one of 10 employees in a company. This month the company will commence holding a charity fundraising raffle at the end of each month. There is only one winner each month. what is the probability that claudia will win the raffle exactly once within the first four months?

for this question would it be 2.8

Ok firstly, just by looking at your answers, they're both wrong because the probability of something happening is always greater than or equal to 0 and less than or equal to 1. Also, in general its just better to express probability as a fraction, not a decimal.
For the first question,

For the second question, its her winning once, losing three times, multiplied by 4 for each month

[amelia20181]

how do you do this

[jamonwindeyer]

how do you do this

Hey! So if you break it down you have:

- 13 married men
- 21 non-married men
- 19 married women
- 13 non-married women

For the first one, there are 34 men and we are picking two, so:



In general, the easiest way to approach any question like this involving multiple selections is to use a tree diagram. So I'd be drawing one of those for this question. It will have two stages, and each stage will have four branches coming off it to match the four groups. Once you put that together you can use it to make the rest of the questions much easier!! It helps visualise how the product/addition rules can be used

[amelia20181]

Thanks! For this question for a can you do 1/5 x 2/9 + 1/5 x 2/9

Mod Edit: Post merge

[jamonwindeyer]

Thanks! For this question for a can you do 1/5 x 2/9 + 1/5 x 2/9

You are welcome!! That's not how I'd approach it, where are you getting that \(\frac{2}{9}\) from?

[amelia20181]

wait how do you do the question

[jamonwindeyer]

wait how do you do the question

Another tree diagram is what I would do! Tree diagram is default response for when you are doing one thing, then another thing, etc. All the probabilities will be \(\frac{1}{5}\) at the first stage, as there are five cards, then \(\frac{1}{4}\) at the second stage, because there are four cards.

Part (a) for D and E, for example, would be:

[amelia20181]

how would you do c for this question

[S200]

100 tickets, 2 prizes.
Each ticket has \(\left(\frac {1} {50} \right ) \) chance of winning a prize.
Anna has 4 tickets.

P= \(\frac {4} {50} \)