Answer:
(a) the new angle the ladder makes with the ground is 
(b) the ladder slipped back about 5 meters
Step-by-step explanation:
Notice that the ladder doesn't change its length in the process.
So let's start from the initial situation , finding the distance from the ground at which the ladder touches the wall when the angle with the ground is 70^o. Notice that this situation is represented by a right angle triangle with the right angle between the wall and the ground (see attached image), and that we can use the sine function to find the side opposite to the 70 degree angle:

therefore 9.4 meters is approximately the height at which the ladder touches the wall initially.
Now, if the tip of the ladder goes down the wall 4 meters, it is now at 9.4 m - 4 m = 5.4 m from the ground. We can therefore use again the sine function to solve for the new angle:

To answer the second question we need to find the original distance from the wall that the bottom of the ladder was originally, and for that we can use the cosine function:

Now fro the new position of the bottom of the ladder relative to the wall:

then the difference in between those two distances is what we need:
8.4 m - 3.4 m = 5 m
<span>The
<u>correct answer</u> is:
350 ml.
Explanation<span>:
Let x be the amount in the fifth container.
The mean is found by adding all of the amounts together and dividing by the number of containers (in this problem, 5). We know that the total from the other 4 containers is 2750; add this to x, our unknown number. Then we divide by 5 to arrive at our answer of 620.
Algebraically,
</span></span>

<span><span>
To solve, multiply both sides by 5:
</span></span>

<span><span>
Subtract 2750 from both sides:
2750+x-2750=3100-2750
x=350.
There are 350 ml in the fifth container.</span></span>
how is the volume of a solution used in calculating concentration?