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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 are 5...
YZ
Answered by Yimin Z. • Maths tutor
5544 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 32/...
HC
Answered by Hal C. • Maths tutor
8248 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, 100%, multiply both sides by 100....
AG
Answered by Andrew G. • Maths tutor
3455 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 all of the po...
EA
Answered by Ellen A. • Maths tutor
3393 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
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