9514 1404 393
Answer:
136
Step-by-step explanation:
The attached chart shows the result of using the numbers in the problem statement to calculate the percentage of the population in each category.
95% accuracy on infected individuals is assumed to mean that 95% of the 2% who are infected return a positive test result. The other 5% return a negative test result.
Similarly, 90% accuracy on uninfected individuals is assumed to mean that 90% of the 98% who are not infected will return a negative test result, and the remaining 10% of those 98% will return a (false) positive test result.
Then of the 11.7% who return a positive test result, only 1.9% are actually infected. This fraction is a/b = 19/117, so ...
a + b = 19 + 117 = 136
_____
<em>Additional comment</em>
When forming ratios of percentages, one must be very clear about the base of the percentage. Above, the base for every percentage is the entire population of mathletes. The fraction 19/117 is the fraction of those who tested positive that are actually infected (about 16.2% of positives).
1935 rounded to the nearest thousand = 2000....because it is closer to 2000 then to 1000.
Hello :
<span>equation of a circle : </span> (x+7)² + (y+6)²=4
Answer:
The function f(x) is positive in the interval (-≠,-2.5) ∪ (1,∞)
Step-by-step explanation:
we have

This is a vertical parabola open upward (the leading coefficient is positive)
The vertex is a minimum
The coordinates of the vertex is the point (h,k)
step 1
Find the vertex of the quadratic function
Factor the leading coefficient 2

Complete the square


Rewrite as perfect squares

The vertex is the point (-\frac{3}{4},-\frac{49}{8})
step 2
Find the x-intercepts (values of x when the value of f(x) is equal to zero)
For f(x)=0



take the square root both sides




therefore
The function f(x) is negative in the interval (-2.5,1)
The function f(x) is positive in the interval (-≠,-2.5) ∪ (1,∞)
see the attached figure to better understand the problem
He loses 9 pts for 90 sec