D because the rest can be divided into cubes or rectangles.
Answer:
15.

16. 10 ml of 20% saline and 40 ml of 10% saline
Step-by-step explanation:
A chemist takes x ml of 20% saline and y ml of 10% saline. In total, he takes
x + y ml that is 50 ml, so

There are
ml of salt in x ml of 20% saline and
ml of salt in 10% saline. There are
ml of salt in 50 ml of 12% saline. Thus,

15. We get the system of two equations:

16. Solve this system. From the first equation:

Substitute it into the second equation:

Answer:
Option D.

Step-by-step explanation:
The area of the circular bases is:

Where
is the radius of the circle
Then


The area of the rectangle is:

Where

b is the width of the rectangle and
is the length
Then the area of the rectangle is:


Finally the total area is:


Answer:
45 eggs left
Step-by-step explanation:
if they had 4 crates and each crate has 18, then we have a total of 72 eggs
subtract 27 eaten eggs from 72
72-27=45
they have 45 eggs left
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