There are a collection of CDs. There are 2 Rock CDs, x Pop CDs and 2x + 5 Jazz CDs. A CD is chosen at random, the probability that it is Rock is 1/20. Work out the probability it is Jazz.

To answer this question first we need to work out how many CDs we have in total. We do this by adding up the number of CDs in each category:Total = 2 + x + 2x + 5.
We can simplify this to give:Total = 3x + 7The probability of a type of CD being picked is equal to the number of CDs in that category divided by the total number of CDs. So lets work with the information we have already:The probability that the CD is Rock is equal to the number of Rock CDs divided by the total number of CDs. This is 2/(3x+7).
But we know from the question that the probability is actually 1/20. So we can set them equal to each other and solve for x:1/20 = 2/(3x+7) Divide both sides by 21/40 = 1/(3x+7) Cross multiple both sides3x+7 = 40 Subtract 7 from both sides3x = 33 Divide both sides by 3x = 11The probability of the CD being Jazz is equal to (2x+5)/(3x+7). Now we just sub in our value for x and we will have the answer:(22+5)/(33+7)=27/40

JM
Answered by James M. Maths tutor

7655 Views

See similar Maths GCSE tutors

Related Maths GCSE answers

All answers ▸

there are 11 sweets in a box four are soft centred and seven hard centred sweets two sweets are selected at random a)calculate the probability that both sweets are hard centred, b) one sweet is soft centred and one sweet is hard centred


A ladder (length 314 cm) is leaning up against a wall. The length between the ladder and the wall is 1.54 m. At what angle is the ladder leaning up against the wall? Round your answer to 2 d.p.


f(x) = 2x + c, g(x) = cx + 5, fg(x) = 6x + d. c and d are constants. Work out the value of d. 3 marks.


Write √98+3√8-√200 in the form a√2, where a is an integer


We're here to help

contact us iconContact ustelephone icon+44 (0) 203 773 6020
Facebook logoInstagram logoLinkedIn logo

© MyTutorWeb Ltd 2013–2025

Terms & Conditions|Privacy Policy
Cookie Preferences