last 2 math problems from barrons book

[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?

 

[jfitzpat]

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?

1. You know that the volumes are the same so, 16 x 10 x 8 = 1280 in^3. Since a cube has identical sides, the length of one side will be the cube root of the volume

2. 33.3/100 of the mixture is at a concentration of .2 while 66.6/100 of the mixture is at a concentration of .4. When you add these togther, you get 33.3% for the total mixture.

 

[mantraman1010]

2. 33.3/100 of the mixture is at a concentration of .2 while 66.6/100 of the mixture is at a concentration of .4. When you add these togther, you get 33.3% for the total mixture.[/QUOTE]


I understand it now. THANKS! You simply think of the total solution as to being divided into thirds since the first addition makes up 1/3 of the solution and the second part makes up 2/3 of the solution. So a third of the solution would have a concentration of 20% and 2/3 of the solution of would have a concentration of 40%. Simply mulitply each percentage with its respective fractional amount in the solution, add them together and you get the answer. (To BodyBldr: Next time you may want to seperate the 331/3 to 33 1/3, it helps. Thanks🙂 )

 

[BodybldgDoc]

thank you