38.82 if you add them all together they give you 95.25
Let x represent the number of liters of 50% acid Theresa puts into the mix. The the number of liters of 30% acid will be (420-x). The total amount of acid in the final solution will be ...
0.50x + 0.30(420-x) = 0.45(420)
0.20x + 126 = 189 . . . . . . . . . . . . . . . simplify
0.20x = 63 . . . . . . . . . . . . . . . . . . . . . subtract 126
x = 63/0.20 = 315 . . . . . . . . . . . . . . . liters of 50% solution
(420-x) = 420-315 = 105 . . . . . . . . . liters of 30% solution
Theresa should mix ...
105 liters of 30% solution
315 liters of 50% solution
Let's think of something that one can hold against a page and draw a circle. Some examples are: a cup, a D battery, a can of soda, the tube from the inside of a paper towel roll, a can of beans, etc.
Think of the can of beans. The part that touches the page (and that you trace around with your pencil) is called a face.What these items have in common is that the faces at the ends are circles (they may or may not be the same size).
The name for this 3-D figure is called a cylinder. Her block, therefore, is a cylinder.
Technically, if the ends were ovals we would still call it a cylinder and so to make sure you have the one with the circles at the ends you would say you have a "right circular cylinder" but for most cases people just say "cylinder" and assume the ends are circles. It really depends what level (elementary, middle school, hs, college) of math you are doing whether just cylinder suffices.
