Answer:
4 ounces
Explanation:
I'm assuming when it says:
% it means 33.3333333333 instead of 33/3.
Anyways under that assumption, we currently have 20 ounces in the grape juice, since 4 ounces is grape juice concentrate and 16 ounces is water. So currently let's just say that the total amount of grape juice concentrate is going to be:
where x is the amount of grape juice concentrate you need to add to make it 33.33%. The next thing to know is how to calculate how much percent a is of b. This can be calculated using the equation:
. So in this case the a is going to be the grape juice concentrate, and the b is going to be the entire mixture (water and grape juice). Since the concentrate is having x added to it, that means the entire thing is also having x added to it. This means we have the equation:
, since we already have 4 ounces of grape juice concentrate, and we already have 20 ounces in total (16 ounces of water + 4 ounces of grape juice). This is going to be equal to 33.33%, or in other words 33 1/3. So to make this a bit easier, I'm going to convert this mixed fraction into one fraction, this gives you the fraction:
. So now that's all left to do is set these two expressions equal to each other and solve for x
Original equation
![(4+x)/(20+x)*100=(100)/(3)](https://img.qammunity.org/2023/formulas/mathematics/high-school/508752nc7a8lroqq46syxrmkaitvwr3xla.png)
Divide both sides by 100
![(4+x)/(20+x)=(100)/(3)/ 100](https://img.qammunity.org/2023/formulas/mathematics/high-school/ze0ugll0icqzqo9n9wbc3u2fmm45tj3d7o.png)
Keep fraction, change division to multiplication, flip 100
![(4+x)/(20+x)=(100)/(3)* (1)/(100)](https://img.qammunity.org/2023/formulas/mathematics/high-school/mdeq64bgxlbvzryiq708jojmrk7g7ovh9d.png)
The 100 in the numerator will cancel out the one in the denominator
![(4+x)/(20+x)=(1)/(3)](https://img.qammunity.org/2023/formulas/mathematics/high-school/flb8ze4659lidkm6c6lbyfvon2aj6ffhbt.png)
Multiply both sides by 20+x
![4+x=(20+x)/(3)](https://img.qammunity.org/2023/formulas/mathematics/high-school/rnc9vsz5x2wzs88y7zn49l110j08xdlxba.png)
Multiply both sides by 3
![3(4+x)=20+x](https://img.qammunity.org/2023/formulas/mathematics/high-school/qkt155iuwpf8ite4zbmtafqecjwkj7tk3n.png)
Distribute the 3
![12+3x=20+x](https://img.qammunity.org/2023/formulas/mathematics/high-school/cuw8ggvs6xnohqvcnbrnw6kavo7rdpn9rs.png)
Subtract x from both sides
![12+2x=20](https://img.qammunity.org/2023/formulas/mathematics/high-school/zmkq8cw7tduqpzsj2dlv7dr5dl7lfpape2.png)
Subtract 12 from both sides
![2x=8](https://img.qammunity.org/2023/formulas/mathematics/high-school/pmnnnr2cbowvoef0ozb3r1b8jifoxn2wcp.png)
Divide both sides by 2
![x=4](https://img.qammunity.org/2023/formulas/mathematics/college/clnezaiwnjqx862gnqh94au9b279p8untt.png)
So Kahn needs to pour 4 more ounces of grape juice, to double check this, since the mixture already has 4 ounces of grape juice, this means the final mixture will have a total of 8 ounces of grape juice concentrate, and a total of 24 ounces, since it already had 16 ounces of water, and 4 ounces of grape juice and now there is 4 more ounces of grape juice being added, so a total of 24 ounces. this means that 8/24 will be grape juice concentrate or in other words:
and when you multiply this by 100 (to convert to percent), you get 100/3 or 33 1/3%