Answer:
3 dogs and 2 cats.
Step-by-step explanation:
In this case we can solve it using a 2x2 system of equations, like this:
let x: number of cats
let y: number of dogs
So:
42.5 * x + 64 * y = 277
35.5 * x + 50.5 * y = 222.5 => x = (222.5 - 50.5 * y) /35.5
Replacing, we are left with that:
42.5 * (222.5 - 50.5 * y) /35.5 + 64 * y = 277
266.37- 60.45 * y + 64 * y = 277
64 * y - 60.45 * y = 277 - 266.37
3.55 * y = 10.63
y = 10.63 / 3.55
y = 2.99, about 3
Now to calculate x:
x = (222.5 - 50.5 * 3) /35.5
x = 2
Which means that it has a total of 3 dogs and 2 cats.
C. multiply because of the order of operations
Let's call our estimate x. It will be the average of n IQ scores. Our average won't usually exactly equal the mean 97. But if we repeated averages over different sets of tests, the mean of our estimate the average would be the same as the mean of a single test,
μ = 97
Variances add, so the standard deviations add in quadrature, like the Pythagorean Theorem in n dimensions. This means the standard deviation of the average x is
σ = 17/√n
We want to be 95% certain
97 - 5 ≤ x ≤ 97 + 5
By the 68-95-99.7 rule, 95% certain means within two standard deviations. That means we're 95% sure that
μ - 2σ ≤ x ≤ μ + 2σ
Comparing to what we want, that's means we have to solve
2σ = 5
2 (17/√n) = 5
√n = 2 (17/5)
n = (34/5)² = 46.24
We better round up.
Answer: We need a sample size of 47 to be 95% certain of being within 5 points of the mean
Answer:
x = 5
Step-by-step explanation:
Maybe you have ...
n(x) = 2x +7
and you want x for n(x) = 17.
17 = 2x +7
10 = 2x . . . . . . subtract 7
5 = x . . . . . . . . divide by 2
Answer:
Step-by-step explanation:
