Step 1 is wrong it should be: 2x - 3x - 1=3
The math club must sell 50 pies in order to reach the goal of 200 dollars
Seventy-three percent is the same as
73% ,
.73 , and
.
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
If the answer is D. the equation to represent the ages of students is:
n + n+1 + n+2 = 45
it is showing that n is the age of one student and the other student has age one year more than the first one and third students has age of 2 years more than first student and one year greater than the second student. if we solve this equation for the value of n, we get;
3n + 3 = 45
3n = 45 -3
3n = 42
n = 14
so the age of one student is 14, second student 15 and third student 16 years.
and if we add there ages, 14 + 15 + 16 = 45
