How Can associative Property be used to mentally find 48+82?

1 answer:

6 0

Associative property of addition represents this equation:
a + b = b + a
So, how would it be helpful with this given equation?
=> 48 + 82
=> Let's start with the ones place value.
(2 + 8) = 10, bring down 0, carry 1 then ( 4 + 8) = 12 + 1 = 13
So the answer is 130.
If we are going to do it vice versa, still expect that the same answer will occur.

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In a sample of 42 water specimens taken from a construction site, 26 contained detectable levels of lead. Construct 90% confiden

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Answer:

(0.4958, 0.7422)

Step-by-step explanation:

Let p be the true proportion of water specimens that contain detectable levels of lead. The point estimate for p is $\hat{p}=26/42=0.6190$ . The estimated standard deviation is given by $\sqrt{\hat{p}(1-\hat{p})/n}=\sqrt{(0.6190)(1-0.6190)/42}=0.0749$ . Because we have a large sample, the 90% confidence interval for p is given by $0.6190\pm z_{0.05}0.0749$ where $z_{0.05}=1.6448$ is the value that satisfies that above this and under the standard normal density there is an area of 0.05. So, the confidence interval is $0.6190\pm (1.6448)(0.0749)$ , i.e., (0.4958, 0.7422).