Approximately 65% of the distribution lies within one standard deviation of the mean, which is to say,
P(72 ≤ x ≤ 86) ≈ 0.65
Normal distributions are symmetric, so the percentage of values one standard deviation below the mean is equal to the percentage of values one standard deviation above the mean.
P(72 ≤ x ≤ 79) = P(79 ≤ x ≤ 86)
but since the sum of these make up P(72 ≤ x ≤ 86), we find
P(72 ≤ x ≤ 79) ≈ 0.65/2 = 0.325
Also due to symmetry, exactly half of the distribution lies to either side of the mean; namely,
P(x ≥ 79) = 0.5
It follows that
P(x ≥ 72) = P(72 ≤ x ≤ 79) + P(79 ≤ x)
P(x ≥ 72) = 0.325 + 0.5
P(x ≥ 72) = 0.825 ≈ 0.84
Answer:
a
Step-by-step explanation:
The numbers are 15 and 10
Step-by-step explanation:
- Let one number be x. Then the other number = 2x - 5. Sum = 25
x + 2x - 5 = 25
3x = 30
⇒ x = 10
⇒ 2x - 5 = 20 - 5 = 15
x/3-3 =x/9+3
add 3 to each side
x/3 = x/9 +6
subtract x/9 from each side
x/3 -x/9 = 6
get a common denominator
3/3*x/3 -x/9 = 6
3x/9 -x/9 =6
2x/9 =6
multiply each side by 9/2
x = 54/2
x=27
