Verified answer

Let the amount of 30% = x

Let the amount of 5% = y

x + y = 25

x*30% + y*5% = 25L* 21%

x*30/100 + y*5/100 = 25*21/100 multiply through by 100

30x + 5y = 21*25 Divide through by 5

6x + y = 105

x + y = 25 Subtract.

5x = 80

x = 16

x + y = 25

16 + y = 25

y = 9

Therefore you need 16 Liters of 30% orange Juice and

9 Liters of 5% orange juice.

Check

=====

30% * 16L + 5 % * 9L =

30/100 * 16 + 5/100 *9 =

4.8 + 0.45

5.25 L of pure orange juice.

21% of 25L = 21/100 * 25 = 5.25 which is what we should get.

Hi,

30x + 5(25 - x) = 21(25)

30x + 125 - 5x = 525

25x = 400

x = 16 liters of 30% orange juice <==ANSWER

25 - x = 25 - 16 = 9 liters of 5% orange juice <==ANSWER

A second way to solve it is with a system of equations using x and y.

x = # liters of 30%

y = # liters of 5%

x + y = 25

.3x + .05y = .21(25)

x + y = 25

30x + 5y = 525

-5( x + y = 25)

30x + 5y = 525

-5x - 5y = -125

30x + 5y = 525

-----------------------

25x = 400

x = 16 liters of 30% OJ

y = 9 liters of 5% OJ

Third really cool way to do it.

Compare the percentages on a number line.

. .5 . . . . . . . . . . . . . . . 21. . . . 30

----+--------------- ----------------+----------+----

. . |<---------------16----------->|<--9--->|

. . |<---------------------------25---------->|

5% was 16/25 of the distance away while the 30% was 9/25 of the distance away.

Reverse these percentages.

Use 9/25 x 25 liters = 9 liters of 5% OJ

Use 16/25 x 25 liters = 16 liters of 30% OJ

I hope that helps!! :-)

Let x be the number of liters of the 30% OJ, so 25-x is the number of liters of the 5% OJ

0.3x + 0.05(25-x) = 0.21(25)

0.3x +1.25 - 0.05x = 5.25

0.25x = 5.25 - 1.25 = 4

x = 16 liters of the 30% OJ

and you need 25-x = 25 - 16 = 9 liters of the 5% OJ.

Check the answer: 30% of 16 liters = 4.8 liters of pure OJ

5% of 9 liters = 0.45 pure OJ liters

The mix will have 4.8 + 0.45 (5.25 liters) pure OJ