Set up a proportion.
The total side of the “top” line is 8 + 10 = 18. The total side of the “bottom” line is 45. This makes the ratio 18/45.
Now we are trying to find the “larger” bottom segment, let it be x. Because the lines are parallel, the ratio of the “larger” top and bottom segments is equal to the ratio of the whole top and bottom lines.
So 18/45 = 10/x
Reduce 2/5 = 10/x
Cross multiply 2x = 50
Solve x = 25
Answer:

And we can find this probability using the normal standard table or excel and we got:

The figure shows the calculation for this case.
Step-by-step explanation:
Previous concepts
Normal distribution, is a "probability distribution that is symmetric about the mean, showing that data near the mean are more frequent in occurrence than data far from the mean".
The Z-score is "a numerical measurement used in statistics of a value's relationship to the mean (average) of a group of values, measured in terms of standard deviations from the mean".
Solution to the problem
Let X the random variable that represent the hardness of a population, and for this case we know the distribution for X is given by:
Where
and 
We are interested on this probability

And the best way to solve this problem is using the normal standard distribution and the z score given by:

If we apply this formula to our probability we got this:

And we can find this probability using the normal standard table or excel and we got:

The figure shows the calculation for this case.
Answer:
15
Step-by-step explanation:
3 counselors for every 20 girls
In this type of calculations, we decompose 13 by checking the lowest powers of the base, that is 40. for example we check 40^2, or 40^3 and compare it to 85
Notice
40*40*40=64,000
so we check how many time does 85 fit into 64,000:
64,000/85=752.94
85*753=64,005; 64000-64,005=-5
this means that

thus

Answer: 10 (mod85)
Remark, the set of all solutions is:
{......-75, 10, 95, .....}, that is 85k +10
Answer:the answeer is
= 72 ft³
Step-by-step explanation:
Multiply the width of the wall by its height. So one of the walls is 80 square feet (10 feet wide x 8 feet high) and the other is 96 square feet (12 feet x 8 feet). If you need the total square footage of the walls - for figuring paint or wallpaper for example - you can simplify the calculation by first adding all the wall lengths together, then multiplying by the height (10 + 12 + 10 + 12 = 44 x 8 = 352 square feet of total wall area).