S1 June 2005 Probability

Im really quite stuck on how to solve the big probability question at the end of this paper. Can anyone help me out? Its the whole question! Here's a the question:

7. In a school there are 148 students in Years 12 and 13 studying Science, Humanities or Arts subjects. Of these students, 89 wear glasses and the others do not. There are 30 Science students of whom 18 wear glasses. The corresponding figures for the Humanities students are 68 and 44 respectively.

A student is chosen at random.

Find the probability that this student

(a) is studying Arts subjects,
(4)
(b) does not wear glasses, given that the student is studying Arts subjects.
(2)

Amongst the Science students, 80% are right-handed. Corresponding percentages for Humanities and Arts students are 75% and 70% respectively.

A student is again chosen at random.

(c) Find the probability that this student is right-handed.
(3)
(d) Given that this student is right-handed, find the probability that the student is studying Science subjects.
(3)

Reply 1

Twiglet

2

lol, loads of people got stuck on that question when I did the exam. I seem to remember drawing lots of Venn diagrams - they always help! I'll have a go at doing them now....

Reply 2

danniella

4

Hello!

Total 148 students

Science: 30 total, 18 glasses, 12 don't
Humanit:112 total, 60 glasses, 44 don't
A r t s : 6 total, 3 glasses, 3 don't

P(arts) = 6/148 = 3/74

P(no glasses/arts) = 3/6 = 0.5

c)
Sci: 30 total, 24 R, 6 Left-handed
Hum:112 total, 84 R, 28 L
Art: 6 total, 4.2 R (?!), 1.8L (ummm... 70% of 6 is definitely 4.2...)

P(R) = 112.2/148 = 561/740
P(science/R) = 24/112.2 = 40/187

Apart from the bizarre number of right-handed arts students...

love danniella

Reply 3

fredthefish

Hi Vai,

You can get a complete solution for that question complete with all the Venn diagrams at
http://www.examsolutions.co.uk/alevel/pastPaperSolutions/Edexcel.php

Reply 4

somaliwarrior

1

Original post by danniella

Hello!

Total 148 students

Science: 30 total, 18 glasses, 12 don't
Humanit:112 total, 60 glasses, 44 don't
A r t s : 6 total, 3 glasses, 3 don't

P(arts) = 6/148 = 3/74

P(no glasses/arts) = 3/6 = 0.5

c)
Sci: 30 total, 24 R, 6 Left-handed
Hum:112 total, 84 R, 28 L
Art: 6 total, 4.2 R (?!), 1.8L (ummm... 70% of 6 is definitely 4.2...)

P(R) = 112.2/148 = 561/740
P(science/R) = 24/112.2 = 40/187

Apart from the bizarre number of right-handed arts students...

love danniella

part a is wrong

S1 June 2005 Probability

Quick Reply

Related discussions

Latest

Trending

Trending

Articles for you