Answer:
4.72 hours/day
Step-by-step explanation:
Mean time spent watching TV (μ) = 2.8 hours a day
Standard deviation (σ) = 1.5 hours a day
The 90th percentile (upper 10%) of a normal distribution has an equivalent z-score of roughly z = 1.282. The minimum time spent watching TV, X, at the 90th percentile is:
On a typical day, you must watch at least 4.72 hours of TV to be in the upper 10%.
Answer:
Step-by-step explanation:
By using the Pythagorean theorem:
b^2+3^2=5^2
b^2+9=25
b=sqrt (25-9)
b=sqrt(16)
b=4
=> 4^2+7^2=c^2
16+49=c^2
65=c^2
=>c=sqrt(65)
c = (approximately) 8
<h3><u>The value of x is 19.</u></h3><h3><u>The value of y is 4.</u></h3>
x = 3 + 4y
x + y = 23
Because we have a value for x we can plug it directly into the second equation.
3 + 4y + y = 23
Subtract 3 from both sides.
4y + y = 20
Combine like terms.
5y = 20
Divide both sides by 5.
y = 4
Plug this value for x back into the original equation.
x = 3 + 4(4)
x = 3 + 16
x = 19
Let 
and 
be the number of elves and reindeers, respectively.
We know that:
(so far 14 of them have arrived)
(each reindeer has 4 legs and each elf has two)
If we multiply the first equation by 2 we have 
, and if we subtract this equation from the second we have 
which implies 
.
So, there are 5 reindeers and 9 elves (remember that they have to sum up to 14).
Expand the brackets. two negatives multiplied together make a positive and a positive and a negative multiplies together make a negative. so you would times everything in the first bracket by -4 and everything in the second bracket by -4 also because it also has a -4 outside the bracket:
4y-4v-20v+4y
