last 2 problems help needed.

[BodybldgDoc]

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hi guys, Been through all the math problems in the barrons book. Cant get these last 2. someone please help. appreciate it.

1. A box has the shape of a rectangular solid, with a base measuring 16 inches by 10 inches and a height of 8 inches. What is the approximate length of the sides of a cubic container having the same volume?
A 9.75 in
B 10.85 in
C 10.00 in
D 12.65 in
E 13.15 in
Answer= B not good at geometry please help

2. If 10 cubic centimeters of 20% acid is mixed with 20 cubic centimeters of 40% acid, the percent of acid in the resulting solution is
A 50
B 30
C 35
D 331/3
E 60
Answer= D hmm?

 

[mantraman1010]

For the first problem you simply take the volume of the the rectangular prism, which is its l x w x h, and take the cube root of the answer because the volume of the cube is s^3. You can use the answer choices to narrow it down, start with the median number and cube it and in this case the 10.85 gives the closest answer. Thats my startegy, yours could be different.

For the second problem I have no idea how the answer is D.

 

[skyNice]

2. If 10 cubic centimeters of 20% acid is mixed with 20 cubic centimeters of 40% acid, the percent of acid in the resulting solution is
A 50
B 30
C 35
D 331/3
E 60
Answer= D hmm?

10 cm^3 of 20% acid: 2 cm^3 of acid and 8 cm^3 of solvent

20 cm^3 of 40% acid: 8 cm^3 of acid and 12 cm^3 of solvent

Mixture of both: 10 cm^3 of acid and 20 cm^3 of solvent

Percent of acid = amount of solute (acid in this case) divided by total amount of solute and solvent

Hence, (10/30) x 100% = 33 1/3 %

 

[BodybldgDoc]

10 cm^3 of 20% acid: 2 cm^3 of acid and 8 cm^3 of solvent

20 cm^3 of 40% acid: 8 cm^3 of acid and 12 cm^3 of solvent

Mixture of both: 10 cm^3 of acid and 20 cm^3 of solvent

Percent of acid = amount of solute (acid in this case) divided by total amount of solute and solvent

Hence, (10/30) x 100% = 33 1/3 %

thanks guys. very nice explanation skynice