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2 years ago

8

2. Given that the radius of the Earth is 6340 Km. calculate the Surface Acer of earth

1 answer:

serious [3.7K]2 years ago

6 0

Answer:

Step-by-step explanation:

The surface area of a sphere (which the earth is considered to be) = 4 pi r^2

pi = 3.14

r = 6340

Area = 4 * 3.14 * 6340 * 6340 = 504856736 square km.

You should either round this to 505,000,000 or express a value in scientific notation.

5.05 * 10^8

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After the release of radioactive material into the atmosphere from a nuclear power plant in a country in 1984, the hay in that

AlexFokin [52]

Answer:

23 days.

Step-by-step explanation:

Let the original amount of radioactive material be 100.

We have been given that the half life of a radioactive material is 8 days. It is safe to feed the hay to cows when 14% of the radioactive isotope remains. We are asked to find the number of days, the farmers need to wait to use the radioactive contaminated hay.

We will use half-life formula to solve our given problem.

$A=a\cdot (\frac{1}{2})^{\frac{t}{h}}$ , where,

A = Amount left after t time,

a = Initial amount,

h = Half-life.

14% of 100 would be 14.

$14=100\cdot (\frac{1}{2})^{\frac{t}{8}}$

$\frac{14}{100}=\frac{100\cdot (0.5)^{\frac{t}{8}}}{100}$

$0.14=(0.5)^{\frac{t}{8}}$

Now, we will take natural log of both sides.

$\text{ln}(0.14)=\text{ln}((0.5)^{\frac{t}{8}})$

Using natural log property $\text{ln}(a^b)=b\cdot \text{ln}(a)$ , we will get:

$\text{ln}(0.14)=\frac{t}{8}\times \text{ln}(0.5)$

$\text{ln}(0.14)=\frac{t\times \text{ln}(0.5)}{8}$

$\frac{\text{ln}(0.14)}{\text{ln}(0.5)}=\frac{t\times \text{ln}(0.5)}{8\times \text{ln}(0.5)}$

$\frac{-1.966112856}{-0.69314718055}=\frac{t}{8}$

$2.836501267=\frac{t}{8}$

$\frac{t}{8}=2.836501267$

$\frac{t}{8}*8=2.836501267*8$

$t=22.6920101377$

$t\approx 23$

Therefore, the farmers need to wait for 23 days.

7 0

3 years ago

You have just bought 4 bottles of water containing 750 ml each. How many litres of water do you have in total?

gulaghasi [49]

You have 187.5 because you divide 750 by 4

8 0

3 years ago

Read 2 more answers

I need help please I don't understand it

german

Answer:

The third and the forth

Step-by-step explanation:

Functions do not have repetition in the x column.

Since the other options have doubles of an x value

(or, to phrase it differently, two y values for one x value)

they are not functions.

3 0

3 years ago

Ethan lives 2 5/12 miles from school. Marquis lives 7/12 mile closer to school than ethan. How far does marquis live from school

goblinko [34]

Answer:

1 5/6 miles

Step-by-step explanation:

first, we take the amout ethan lives from school, and turn it into a mixed number

2 5/12 = 29/12

marquis lived 7/12 mile closer

so, we have to subtract that from how far away ethan lives

29/12 - 7/12 = 22/12

22/12 simplified is 1 10/12 or 1 5/6

7 0

2 years ago

Tammy accidentally wrote a check for more money than she had in her checking account. When she got her statement, she saw that h

sergejj [24]

Answer:

-100

Step-by-step explanation:

1/5 of -125 will be -25.

So, if she deposits 1/5 of what she owes, then she will deposit $25.

Her balance will then become -100 because she paid back 25.

Her new balance is -100

7 0

3 years ago