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Sveta_85 [38]
4 years ago
14

A 20mg sample of thorium-233 decays to 17mg after 5 min. determine the half life of thorium-233?

Mathematics
1 answer:
snow_tiger [21]4 years ago
3 0
Let r be the decay rate (time in minutes) 17 = 20 e^(5r) 0.85 = e^(5r) ln 0.85 = 5r similarly, ln 0.5 = hr ... where h is the half-life, so dividing the 2 equations, ln 0.85 / ln 0.50 = 5r / hr = 5/h h = 5 ln 0.50 / ln 0.85 h = 21.3 min b) 1/20 = 0.05, so ln 0.85 = 5r ln 0.05 = tr t = 5 ln 0.05 / ln 0.85 t = 92.2 min
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http://goblues.org/faculty/grantm/files/2015/12/Practice-Test-3.7-Solutions.pdf

I think it's question number three. Sorry if the link dosen't work.

4 0
3 years ago
If the radius of mars is about 13.7% of neptune's radius, what is the radius of neptune?
Marianna [84]
The volumetric mean radius of Mars is about 3389.5 km. We know that it's 13.7% of Neptune's mean radius, so we can write it down as:

3389.5 = 13.7% of x (where x is Neptune's radius)
3389.5 = 13.7% x
3389.5 = 137/1000x                / * 1000 (both sides)
3389500 = 137x                       / ÷ 137 (both sides)
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Answer: The mean radius of Neptune is about 24740.88 km.
6 0
3 years ago
Can someone help me again with these math work?
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7 0
3 years ago
Read 2 more answers
the product of two whole numbers is 36 . what is the greatest possible sum that the number can have?​
ch4aika [34]

Whole numbers are positive numbers without decimals.  First, list all the whole number factors of 36:

1 and 36

2 and 18

3 and 12

4 and 9

6 and 6

Next, see which one of those pairs has the highest sum:

1+36=37

2+18=20

3+12=15

4+9=13

6+6=12

The greatest possible sum the numbers can have is 37.

Hope this helps!!

3 0
3 years ago
You are trying to bulk and gain muscle. Your trainer says your daily calorie intake should increases based on hours you spend ex
s2008m [1.1K]

a) T - Calories, 2000 - <em>Minimum</em> calories, 500 - Additional calories per exercise hour, b) We should consume 3500 calories to spend three hours exercising.

<h3>How to analyse a linear function of calorie gain in terms of the exercise time</h3>

In this question we have a <em>linear</em> function where the <em>independent</em> variable is the exercise time (h), in hours, and the <em>dependent</em> variable is the calorie gain (T), in calories. The constant "2000" is the <em>minimum</em> calorie consumption and the constant "500" represents the amount of <em>additional</em> calories per each hour of exercise.

Now we proceed to respond the questions of the part a):

(i) T - Amount of calories needed, (ii) 2000 - Minimum calorie consumption, (iii) 500 - Amount of additional calories per hour of exercise.

b) And lastly we calculate the amount of calories by evaluating the function:

T = 2000 + 500 · 3

T = 2000 + 1500

T = 3500

We should consume 3500 calories to spend three hours exercising.

<h3>Remark</h3>

The statement is incomplete, the complete form is shown below:

You are trying to bulk up and gain muscle. Your trainer says that your daily calorie intake should increase based on the hours you spend exercising and can be represented by the following equation: T = 2000 +  500 · h

a) What does each part of this expression represent? (i) T = , (ii) 2000, (iii) 500, (iv) h

b) If you spend 3 hours exercising, how many calories should you consume?

To learn more on linear functions: brainly.com/question/21107621

#SPJ1

4 0
2 years ago
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