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3 years ago

A sample of radium has a weight of 1.5 mg and decays

Mathematics

1 answer:

Oliga [24]3 years ago

6 0

Answer: $(b)$

Step-by-step explanation:

Given

Initial mass of radium is $A_o=1.5\ mg$

It decays by half every 6 years i.e. $T_{\frac{1}{2}}=6$

For radioactive decay, sample at any time is given by

$\Rightarrow A=A_o2^{-\dfrac{t}{T_{\frac{1}{2}}}}$

Insert the values

$\Rightarrow A=1.5\cdot 2^{\dfrac{-t}{6}}\\\\\Rightarrow A=1.5\cdot \left(\dfrac{1}{2}\right)^{\dfrac{-t}{6}}\\\\\Rightarrow A=1.5\cdot (0.5)^{\dfrac{t}{6}}$

Thus, option (b) is correct.

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Damm [24]

Answer:

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Step-by-step explanation:

The axes on your graph are not labeled, so we have to assume they follow the usual convention. That is, the vertical axis is the y-axis, and the horizontal axis is the x-axis.

The x-coordinate tells how far to the left or right of the y-axis the point is. Here, point L is 1 grid square to the left of the vertical line that is the y-axis. If you follow the vertical line through L down to where it crosses the x-axis, you will see an unlabeled open circle there. (We don't know the purpose of that circle, but we call it to your attention so you know you're looking in the right place.)

Looking 4 more grid squares to the left of that point, you see the marking "-5". This tells you each grid square corresponds to one unit. Then the first one to the left of the y-axis (where the open circle is) has a value of -1. That is the value of the x-coordinate of point L.

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1. At the gym on Monday, Larry is told to up his weight on the bench-press by 15% from last week. Last week he was bench-pressin

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Answer:

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Step-by-step explanation:

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In a study of the impact of smoking on birth weight, researchers analyze birth weights (in grams) for babies born to 189 women w

kompoz [17]

Answer:

c. Smoking is associated with lower birth weights. When smokers are compared to nonsmokers, we are 95% confident that the mean weight of babies born to nonsmokers will be between 76.5 grams to 486.9 grams more than the mean birth weight of babies born to smokers.

Step-by-step explanation:

The difference in mean birth weights (nonsmokers minus smokers) is 281.7 grams with a margin of error of 205.2 grams with 95% confidence.

Then, we know that the 95% confidence interval is (76.5, 486.9)

$LL=M-MOE=281.7-205.2=76.5\\\\UL=M-MOE=281.7+205.2=486.9$

a. We are 95% confident that smoking causes lower birth weights by an average of between 76.5 grams to 486.9 grams.

False, it interprets the confidence interval as a probability for individual cases. The confidence interval is a range for the population mean.

b. There is a 95% chance that if a woman smokes during pregnancy her baby will weigh between 76.5 grams to 486.9 grams less than if she did not smoke.

False, it interprets the confidence interval as a probability for individual cases. The confidence interval is a range for the population mean.

c. Smoking is associated with lower birth weights. When smokers are compared to nonsmokers, we are 95% confident that the mean weight of babies born to nonsmokers will be between 76.5 grams to 486.9 grams more than the mean birth weight of babies born to smokers.

True.

d. With such a large margin of error, this study does not suggest that there is a difference in mean birth weights when we compare smokers to nonsmokers.

There is enough evidence, as the lower bound of the confidence is positive. This means that there is only a probability of 0.05/2=0.025 that the true mean weight difference is smaller than 76.5 grams.

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