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Maths
GCSE

Hannah's sweet problem (Edexcel 2015): There are n sweets, 6 are orange, rest of the sweets are yellow. She takes 2 sweets randomly without replacing them and the probability that 2 orange sweets are chosen is 1/3. Show that n^2-n-90 = 0.

Draw a probability tree diagram. For this question, only two branches are required (orange and orange). At the start, there are n sweets in total, 6 are orange, so p(O) = 6/n. On our second pick, there ar...

YZ
Answered by Yimin Z. Maths tutor
4657 Views

Karen got 32 out of 80 in a maths test. She got 38% in an English test. Karen wants to know if she got a higher percentage in maths or in English. Did Karen get a higher percentage in maths or in English?

We are given that Karen got 38% in her English test, so all that's left to do is work out the percentage she achieved in her maths test and then compare it with 38%: We calculate the percentage by taking ...

HC
Answered by Hal C. Maths tutor
7090 Views

If a shop sells a bucket at £16 after a 15% discount, how much would the bucket have been before the discount?

Define the original cost as 100%.

So £16=85% (100-15) of the original cost.

Find 1% of the original cost by dividing both sides by 85. 

16/85=85/85%

To find the orginal cost, 1...

AG
Answered by Andrew G. Maths tutor
2875 Views

One of the teachers at a school is chosen at random. The probability that this teacher is female is 3/5. There are 36 male teachers at the school. Work out the total number of teachers at the school.

So we know that 3/5 teachers in the school are female, and we also know that 36 teachers are male. 

The first thing to note is that if 3/5 are female, that leaves 2/5 to be male. This is because al...

EA
Answered by Ellen A. Maths tutor
2768 Views

Differentiate sin(x)cos(x)

let sin(x)=u , let cos(x)=v

du/dx = cos(x),   dv/dx = -sin(x)

d[sin(x)cos(x)]/dx = v.du/dx + u.dv/dx

= cos^2(x) - sin^2(x)

JD
Answered by James D. Maths tutor
4776 Views

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