Maths calculator paper tommorrow!

Hey I'm really stuck on this question, if someone could help me I'd love you forever!! Here's the question:
Bob and Anne play a game.
Bow will take a counter at random from the bag.
He will record the colour and put the counter back in the bag.
Anne will then take a counter at random from the bag.
She will record it's colour.
The probability that Bob's counter is red and Anne's counter is not red is 14/81.
c) Prove that 19n^2 - 124n - 224 = 0

Good luck to everyone else taking this paper!

Reply 1

Happyness

You can just simply solve the quadratic...use the quadratic formula for solving the equation..

Reply 2

calcium878

Yep, just plug numbers into the good old quadratic formula, accepting the positive answer

Reply 3

TheRandomer

What does 'n' stand for then? =/

n is the variable

Ok. see solving the equation is what I would have done except that part a) of the question was 'solve the equation'. Surely they wouldn't ask for the same thing twice in 1 question? Thats what got me confused about whether they were asking for something different.

Reply 6

TheRandomer

calcium878

n is the variable

well, of course. but in terms of the probability. is it the number of things in the bag, the number of red ones...?

Reply 7

username43524

heres another question for revision Question 8 on 2005 calc paper

its a 4-point moving averages question

thought i'd start off the revision for tomorrow in this thread instead of starting a new one

i'll do the question then post what i get, and compare with others, taht way people can see where they go wrong and have the right answer explained to them

Reply 8

username43524

i plotted the points on the graph at 1st
then got £103
i did a line of best fit and worked out that the next 4-point would be 99
the did 99x4=396
94+98+101=293
396-293 = 103

not sure if that is right or not?

Reply 9

tiger_vio

GOOD LORD.
Me and my dad just did part a,b,c and d of that question- took us half an hour! The process is SO long!
Draw a probabilty tree.

First 3 branches will be red, white, and blue. Red will be n/4(n+1), blue is n+2/4(n+1) and white is 2n+2/4(n+1). Then draw another 3 branches for all of those, and work out:
P(r and b)
P (r and w)

It will take you forever, trust me! It took me 2 sides of A4 paper :tongue: