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Delvig [45]
2 years ago
8

If 3.0 grams of strontium-90 in a rock sample remained in 1989, approximately how many grams of strontium-90 were present in the

original rock sample in 1933?
Mathematics
1 answer:
kirill [66]2 years ago
5 0

Answer:

<em>11.29 grams </em><em>of strontium-90 were present in the original rock sample in 1933.</em>

Step-by-step explanation:

Strontium has a half-life of 28.8 years. Therefore,

1989 - 1933 = 56 years.

56 / 28.8 = 1.94 half-lives

Thus, the quantity of the radioisotope remaining will double for each half-life elapsed. moving backwards in time.

Therefore, moving backwards in time by 1.94 half-lives, the quantity remaining will double by 1.94 times.

Thus, the amount remaining in 1933 is

3.0 × (1.94)² = <em>11.29 grams</em>

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Astrid wants to buy pumpkins and watermelons. She wants to buy more than 101010 fruits, and she has a budget of \$117$117dollar
julsineya [31]

Answer:

D 5 pumpkins, 13 watermelons

Step-by-step explanation:

please give brainiest

0 pumpkins, 0 watermelons

7 pumpkins, 3 watermelons

5 pumpkins, 13 watermelons

5 pumpkins, 5 watermelons

3 0
2 years ago
Mathew got 20 pencils, 3 rulers, 12 erasers,11 pens, 24 notebooks, 8 files, and 11 paper clips from a stationery shop for his br
Damm [24]

Answer:

89

Step-by-step explanation:He bought 89 items because 20 + 3 is 23, 23 + 12 is 35, 35 + 11 is 46, 46 + 24 is 70, and 70 + 11 is 89.

3 0
2 years ago
A statistics instructor who teaches a lecture section of 160 students wants to determine whether students have more difficulty w
Leona [35]

Answer:

There is no evidence that there is no significant difference between the sample means

Step-by-step explanation:

given that a  statistics instructor who teaches a lecture section of 160 students wants to determine whether students have more difficulty with one-tailed hypothesis tests or with two-tailed hypothesis tests. On the next exam, 80 of the students, chosen at random, get a version of the exam with a 10-point question that requires a one-tailed test. The other 80 students get a question that is identical except that it requires a two-tailed test. The one-tailed students average 7.81 points, and their standard deviation is 1.06 points

The two-tailed students average 7.64 points, and their standard deviation is 1.33 points.

Group   One tailed X     Two tailed Y  

Mean 7.8100 7.6400

SD 1.0600 1.3300

SEM 0.1185 0.1487

N 80       80  

H_0:\bar x=\bar y\\H_a: \bar x \neq \bar y

(Two tailed test)

The mean of One tailed X minus Two tailed Y equals 0.1700

t = 0.8940

 df = 158

p value =0.3727

 p is greater than alpha 0.05

There is no evidence that there is no significant difference between the sample means

3 0
2 years ago
NEED HELP ON NUMBER 13 AND 14
Kazeer [188]

Answer:

Question 13: For age groups y=1 and y=1.3 response is 8 microseconds.

Question 14: The club was making a loss between 11.28 and 4.88 years.

Step-by-step explanation:

Question 13:

The age group y for which the response rate R is 8 microseconds  is given by the solution of the equation

8=y^4 +2y^3 - 4y^2 -5y +14.

We graph this equation and find the solutions to be

y=1;   y=1.302;     y=-2;    y=-2.302.

Since only positive solutions for y are valid in the real world we take only those.

Thus only for age groups y=1 and y=1.3 the response is 8 microseconds.

Question 14:

The footbal club is making a loss when p(t)

Or

t^3 -14t^2 +20t +120

We graph this inequality and find the solutions to be

t and 4.88

Since in the real world only positive values for t are valid, we take the the second solution to be true.

Thus the club was making a loss in years 4.88

5 0
2 years ago
SOLVE PLEASE Sarah must maintain a balance of at least $500 in her checking account to avoid finance charges. If her current bal
dem82 [27]
So since her balance must be at least 500, her ballance cannot reach 500
so 794-500=294
see how many 25's you can fit into 294
we know that 4 25's =100 and 294 is roughly 300
so 4 times 3=12
we minus one of the 25's because 294 is less than 300 so
the innequality is
>means more than
794-25x>500
5 0
2 years ago
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