<PRE><B>Question 1160735</B>
A group of friends go out for supper one evening.
 They decide to share the bill which comes to R960.
 However, two of them forget their wallets and cannot pay.
 The remaining friends each now have to pay an extra R40 to cover the cost.
 How many friends are in the group?
:
let x = no. of friends
then
(x-2) = no. that paid
and
{{{960/x}}} = amt paid if each paid their share
:
{{{960/(x-2)}}} - 40 = {{{960/x}}}
multiply by x(x-2)
960x - 40x(x-2) = 960(x-2)
960x - 40x^2 + 80x = 960x - 1920 
subtract 960x from both side
-40x^2 + 80x + 1920 = 0
simplify, divide by -40
x^2 - 2x - 48 = 0
Factors to
(x-8)(x+6) = 0
positive solution
x = 8 friends
:
:
Check this
If all paid: 960/8 = 120
If six paid: 960/6 = 160
-------------------------
6 friends ea pd more: 40,  total of 240 to cover 2 unpaying friends 
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