Answer:
Step-by-step explanation:
The formula for determining the sum of the first n terms of an arithmetic sequence is expressed as
Sn = n/2[2a + (n - 1)d]
Where
n represents the number of terms in the arithmetic sequence.
d represents the common difference of the terms in the arithmetic sequence.
a represents the first term of the arithmetic sequence.
If a = 5, the expression for the sum of the first 12 terms is
S12 = 12/2[2 × 5 + (12 - 1)d]
S12 = 6[10 + 11d]
S12 = 60 + 66d
Also, the expression for the sum of the first 3 terms is
S3 = 3/2[2 × 5 + (3 - 1)d]
S3 = 1.5[10 + 2d]
S3 = 15 + 3d
The sum of the first 12 terms is equal to ten times the sum of the first 3 terms. Therefore,
60 + 66d = 10(15 + 3d)
60 + 66d = 150 + 30d
66d + 30d = 150 - 60
36d = 90
d = 90/36
d = 2.5
For S20,
S20 = 20/2[2 × 5 + (20 - 1)2.5]
S20 = 10[10 + 47.5)
S20 = 10 × 57.5 = 575
Answer:
147°
Step-by-step explanation:
106°+139°+126°+141°+112°+129°+x =900°
753°+x = 900°
x = 900°-753°
x= 147° (sum of the interior angles of a heptagon=900°)
Answer:
3 hours
Step-by-step explanation:
60 x 60 = 3,600 x 3 = 10800
Answer:
5.2 inches
Step-by-step explanation:
The diameter of small Nerf balls follows normally distribution with mean 5.2 inches and standard deviation 0.08 inches.
We have to calculate the mean of sampling distribution when 20 balls are selected randomly.
Here, μ=5.2 and σ=0.08.
We know that mean of sampling distribution for mean is equal to the population mean.
mean of sampling distribution for mean= μxbar=μ= 5.2
Thus, mean of the sampling distribution of the sample mean is 5.2 inches
