Which expression represents the sum (7z−15)+(8−6z)
2 answers:
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To find which of the following roots is between "8" and "7" we can calculate the root of which numbers result in 8 and 7. To do this we will power them by 2, this is done because power is the oposite operation to the root. Doing this gives us:
So the root of 64 is 8 and the root of 49 is 7. We need to find the number that is between 49 and 64.
From the options the only one that qualifies is 52. The correct option is b.
Answer:
Hence,we need at least 136 rainfall PH values in the sample i.e
n ≥ 136
Step-by-step explanation:
We are given that:
(σ1)^2 = (σ2)^2 = Population variance = 0.25
So, E < 0.1
Confidence coefficient (c) = 0.9
n = n1 = n2
For confidence level, 1 - α = 0.9,we'll determine Z (α /2) = Z 0.05 by looking up 0.005 using the normal probability table which i have attached.
So, Z (α /2) = 1.645
The margin of error E is given as;
E = Z (α /2)√[(σ1)^2)/n1] + [(σ2)^2)/n2]
= Z (α /2)√({(σ1)^2 + (σ2)^2}/n) < 0.1
Multiply both sides by √n to get;
Z (α /2)√(σ1)^2 + (σ2)^2} < 0.1√n
Divide both sides by 0.1;
{Z (α /2)√(σ1)^2 + (σ2)^2}}/0.1 <√n
When we square each side, we get
{Z (α /2)√(σ1)^2 + (σ2)^2}}/0.1} ^2 < n
We'll now fill in the known values and solve;
n > ( 1.645 x √{(0.25 + 0.25)/0.1}^2
n > 135.3 or approximately n > 136
Hence,we need at least 136 observations in the sample i.e
n ≥ 136
