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remember a(b+c)=ab+ac
8(y+4)=8(y)+8(4)=8y+32
8y+32=7y+38
minus 7y both sides
y+32=38
mius 32 oth sides
y=6
Answer: c. elm
Step-by-step explanation:
Given : The circumference of the oak tree= 0.539 meters
=
[∵ 1 m = 100 cm] (1)
The circumference of the ash tree= 0.509 yards
[∵ 1 yard = 3 feet]
[∵ 1 foot = 30.48 cm]
(2)
The circumference of the elm tree = 6281.70 millimeters
(3)
The circumference of the poplar tree = 0.000385 miles
[∵ 1 mile = 5280 feet]
[∵ 1 foot = 30.48 cm]
(4)
From (1) , (2) , (3 ) and (4) it is clear that
46.54< 53.9 < 61.96 < 628.17
Hence, the elm tree has the greatest circumference.
<span>n = 5
The formula for the confidence interval (CI) is
CI = m ± z*d/sqrt(n)
where
CI = confidence interval
m = mean
z = z value in standard normal table for desired confidence
n = number of samples
Since we want a 95% confidence interval, we need to divide that in half to get
95/2 = 47.5
Looking up 0.475 in a standard normal table gives us a z value of 1.96
Since we want the margin of error to be ± 0.0001, we want the expression ± z*d/sqrt(n) to also be ± 0.0001. And to simplify things, we can omit the ± and use the formula
0.0001 = z*d/sqrt(n)
Substitute the value z that we looked up, and get
0.0001 = 1.96*d/sqrt(n)
Substitute the standard deviation that we were given and
0.0001 = 1.96*0.001/sqrt(n)
0.0001 = 0.00196/sqrt(n)
Solve for n
0.0001*sqrt(n) = 0.00196
sqrt(n) = 19.6
n = 4.427188724
Since you can't have a fractional value for n, then n should be at least 5 for a 95% confidence interval that the measured mean is within 0.0001 grams of the correct mass.</span>
