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Mathematics 14 Online
OpenStudy (anonymous):

http://www.xtremepapers.com/papers/CIE/Cambridge%20IGCSE/Mathematics%20(0580)/0580_s07_qp_4.pdf Question8 (e) plz

OpenStudy (anonymous):

Simply x+x+4

jhonyy9 (jhonyy9):

so you need to calcule first the mean mass of a chokolate is 105/x gramms the mean mass of a toffe will be 105/(x+4) so and you know again that the difference of 105/x and 105/(x+4) equal 0,8 gramms

jhonyy9 (jhonyy9):

so from this i think that you will can calcule easy the x

jhonyy9 (jhonyy9):

and x^2 +4x -525 =0 so this quadratic equation i think that you can solving easy using the formula what you know or factorizing it or using the formula of discriminant and the formula of roots so will can you calcule it ?

OpenStudy (anonymous):

x=21,-25

jhonyy9 (jhonyy9):

so i think it invers -21 and 25

OpenStudy (anonymous):

But in the answer scheme is -21,25 for(d) and the answer is 46 for(e)

jhonyy9 (jhonyy9):

check your calcules please because the right answer need being -21 and 25 so because from this quadratic equation b=+4 and not is -4 than the difference of these roots need being +4 and not how you have got it with 21 and -25 because with these roots the differenec is -4

jhonyy9 (jhonyy9):

ok ?

OpenStudy (anonymous):

what?

jhonyy9 (jhonyy9):

why need to be -21 and 25 and not invers 21 and -25 ok ?

OpenStudy (anonymous):

oh my mistake Its 21,-25

jhonyy9 (jhonyy9):

so than now all is well ?

OpenStudy (anonymous):

but how to find (e)

jhonyy9 (jhonyy9):

so you know that the total mass of chocolats is 105 gramms and the total mass of toffees is the same 105 gramms too so but you have calculated that a chocolate has a mass of ... and a toffee has a mass of ... so using thses resultes you can calcule easy how many chocolates and how many toffes are in box total ok ?

OpenStudy (anonymous):

Can u show me so i can understand more

OpenStudy (anonymous):

plzz

jhonyy9 (jhonyy9):

so you have solved c. right sure ?

OpenStudy (anonymous):

yes sure

jhonyy9 (jhonyy9):

there is 105 105 ---- - ----- = 0,8 x x+4 so you have got it the same ?

OpenStudy (anonymous):

yes

jhonyy9 (jhonyy9):

ok than please solve this here now

jhonyy9 (jhonyy9):

this will be the second part of C.

OpenStudy (anonymous):

\[0.8^{2}-3.2x+420\]

jhonyy9 (jhonyy9):

not is right step by step please

OpenStudy (anonymous):

ok

OpenStudy (anonymous):

\[\frac{ 105 }{ x }=0.8+\frac{ 105 }{ x-4 }\]

jhonyy9 (jhonyy9):

why ? how you add two fractions with denominator difference so if you check it there the denominator common will be x^2 +4x

OpenStudy (anonymous):

I am not going to add 0.8 with 105/x-4 but first I am going to unite the denominators first which are x-4 and 1

jhonyy9 (jhonyy9):

no there we have 105 105 ---- - ----- =0,8 x x+4 so first you need calcule this step by step ok ?

jhonyy9 (jhonyy9):

because if you read the second line from point c. so you need to show that will get .....

jhonyy9 (jhonyy9):

so you dont like continue it ?

OpenStudy (anonymous):

i just want to find (e) and its method

jhonyy9 (jhonyy9):

ok so than if you see there you have got like roots of thie quadratic equation the -21 and 25 so what mean these numbers ?

OpenStudy (anonymous):

the mean i guess

jhonyy9 (jhonyy9):

@imron07 you have wrote the right answer in your first reply can you rewrite it here ?

OpenStudy (anonymous):

x=21,-25

jhonyy9 (jhonyy9):

invers -21 and 25

OpenStudy (anonymous):

sorry

jhonyy9 (jhonyy9):

so what is your answer for point (d) ?

OpenStudy (anonymous):

\[(x+25)(x-21)\]

jhonyy9 (jhonyy9):

this is sure ???? so because not is right ...

OpenStudy (anonymous):

why?? this is not correct

jhonyy9 (jhonyy9):

because the formula say that ax^2 +bx +c=(x-x1)(x-x2) where x1 and x2 are roots of quadratic equation so if i remember right ???

OpenStudy (anonymous):

but in the answer scheme its written (x+25)(x-21)

OpenStudy (anonymous):

and i checked using the calculator and its correct

jhonyy9 (jhonyy9):

ok but answer on your question for point (e) will be 21+25 =46 this is because the number of terms from a box not can being negativ so hence you need just assuming these pieces of toffes and chocolates

jhonyy9 (jhonyy9):

so suppose that is show like in the point c. that 105/x -105/(x+4) =0,8 will result the same equation like have wrote there and that this resulted roots are the same 25 0nd -21 so supposed this right you can calcule the numbers of chocolates and toffees assuming 25 to 21 because you know that 105 gramms has a total sum of chocolates and the same 105 gramms has a total sum of toffes minus 4 what will be 25-4 =21 so hence the total sum of toffees and chocolates will be 21 +25 =46 ok ?

OpenStudy (anonymous):

ok thank u

jhonyy9 (jhonyy9):

sure you have understood it right all ?

OpenStudy (anonymous):

yes

jhonyy9 (jhonyy9):

ok than good luck bye

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