Is Anyone On Here Good At Math? I Needed Help With This Question.

[Elena_W]

A cafe sells 2 types of coffee, one for $7.90 per kilo, the other for $9.40 per kilo. If the store owner mixes 20 kilos and intends to sell the mixture for $8.5 per kilo, how many kilos of each brand should she use to make the same revenue as if the 2 brands were sold unmixed?

[Prudie]

20 kg at $8.5 will bring in $170
You need to know how many of the 7.90 (say x) and how many of the 9.4(say y) will make 170 if we know x+y is 20kg
Your 2 equations are therefore:

X + Y = 20
7.9X + 9.4Y = 170

From the 1st equation substitute Y= 20 –X in the 2nd to give;

7.9X + 9.4(20-X) = 170

I think you’ll find that will give you
X=12 and Y = 8

[zebo]

X of the $7.90 and y of the $9.40

x + y = 20 (the total to be made)

7.9x + 9.4y = 20 x 8.5 ( 170, the cost of the new batch)

7.9x + 7.9y = 158 (20 x 7.9) everything x by 7,.9

9.4y - 7.9y = 170 – 158 (12) (The x terms cancel each other out)

1.5y = 12

y = 12/1.5 = 8

x = 20 – 8 = 12

[zebo]

Glad someone else agrees! Trying to recall the ratio method too.

[Prudie]

Ditto! very reassuring ;-)

[Elena_W]

I just wanted to say thank you to both of you for helping me out, i really appreciate it!!

[Baldric]

http://www.theanswerbank.co.uk/Jobs-and-Education/Question1444387.html