DESTROYER: QR #67 help!

[Mrbubbles]

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#67. "Gary mixes 4 oz of run with a certain quantity of cola. The rum is 40% alcohol by volume. If the drink is to be 16% alcohol by volume, how much cola is needed?"


A: the answer is 6 oz of cola.

the explanation is SO wierd.
i don't understand where they get the FOUR when they do .40(4)=.16B
i know it's the oz of rum, but i just don't get it.

explain please! =)

 

[vDDmaniaC]

#67. "Gary mixes 4 oz of run with a certain quantity of cola. The rum is 40% alcohol by volume. If the drink is to be 16% alcohol by volume, how much cola is needed?"


A: the answer is 6 oz of cola.

the explanation is SO wierd.
i don't understand where they get the FOUR when they do .40(4)=.16B
i know it's the oz of rum, but i just don't get it.

explain please! =)

I try my best to explain this.
What I did was to simplified first.
Set the equation first.

Rum: 4oz
cola: x (let's set like this for now)
Mixture:y
4+x=y agree?
y wants to be 16% OH so we can use M here. y*0.16
4oz (rum) is 40$ OH so we can use M here as well, 4*0.4
Since they are mixed together, they have to be the same
0.16y=1.6
y=10

Since mixture 10. cola should be 10-4=6

This is how I did.

Hope it helps

 

[Mrbubbles]

I try my best to explain this.
What I did was to simplified first.
Set the equation first.

Rum: 4oz
cola: x (let's set like this for now)
Mixture:y
4+x=y agree?
y wants to be 16% OH so we can use M here. y*0.16
4oz (rum) is 40$ OH so we can use M here as well, 4*0.4
Since they are mixed together, they have to be the same
0.16y=1.6
y=10

Since mixture 10. cola should be 10-4=6


This is how I did.

Hope it helps

.... i understand the Total X 16% (or y*.016), because you want the total amount (rum + cola) to be 16 % alcohol.

I don't undderstand why they equal this amount to the 4oz * 40%. it just doens't make sense..logically. i understand why u subtract 10 to get cola ..just not that part.

 

[jdent]

I thought that it was weird also but it is a very important problem to understand the steps and logic behind just know it.

 

[Streetwolf]

4 oz rum at 40% alcohol by volume. Don't you drink? That means there are 4 oz of fluid but only 40% of it contains alcohol. The rest is not alcohol.

So 4*0.4 = 1.6 oz, represents the amount of alcohol in the rum. So with just 4 oz of that brand of rum (strong rum!), you have 1.6 oz of alcohol (40%).

You want your drink to be 16% alcohol. Since you are adding a non-alcoholic liquid, your total amount of alcohol in the end is still going to be 1.6 oz. For this to be 16%, you would need to have 10 oz of liquid (8.4 oz non-alcoholic + 1.6 oz alcoholic). Since you have 4 oz from the rum and you want 10 oz total, you need to add 6 oz of cola.

 

[topdent1]

DUDE...i hate this problem soooo much!

 

[Mrbubbles]

4 oz rum at 40% alcohol by volume. Don't you drink? That means there are 4 oz of fluid but only 40% of it contains alcohol. The rest is not alcohol.

So 4*0.4 = 1.6 oz, represents the amount of alcohol in the rum. So with just 4 oz of that brand of rum (strong rum!), you have 1.6 oz of alcohol (40%).

You want your drink to be 16% alcohol. Since you are adding a non-alcoholic liquid, your total amount of alcohol in the end is still going to be 1.6 oz. For this to be 16%, you would need to have 10 oz of liquid (8.4 oz non-alcoholic + 1.6 oz alcoholic). Since you have 4 oz from the rum and you want 10 oz total, you need to add 6 oz of cola.

WOW thank you! that tottttally makes sense now. except i still would not have known to set up the problem like that. thanks homie =)