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Aleks [24]
3 years ago
9

a radioactive substance has a half-life of 2 seconds. A scientist begins with a sample of 20 grams. How much of the substance re

mains after 8 seconds?
Mathematics
1 answer:
s344n2d4d5 [400]3 years ago
5 0

Answer:

1.25 g

Step-by-step explanation:

you start with 20g at 0 seconds.

divide by half after 2 seconds and you have 10g.

at 4 seconds you have 5g.

at 6 seconds you have 2.5g.

at 8 seconds you have 1.25g.

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Four of the angle of a Pentagon are 70°,90°,100° and 145°. What is the side of a fifth angle?​
dezoksy [38]

Answer: 135°

Step-by-step explanation:

The sum of the angles in a pentagon is equal to 540°, and the sum of the first four angles is 405°.

70 + 90 + 100 + 145 = 405

540 - 405 = 135

6 0
3 years ago
A gear in a machine turns 2 1/2 times every hour.
givi [52]
We can solve this by multiplying those two numbers but we place them in improper fraction.

2 1/2 x 2 1/4
becomes
5/2 x 9/4

for fraction multiplication, just multiply numerator by numerator and denominator by denominator

5/2 x 9/4 = 45/8

we can simplify this into mixed fraction while numbers in whole numbers and remainder in numerator

5 5/8 is the answer
6 0
4 years ago
John who is 5 ft tall is standing 20 feet away from a tree, and you measure the angle of elevation to be 38∘. How tall is the tr
fenix001 [56]

Answer:

The tree is 20.6 ft tall.

Step-by-step explanation:

Please check the attached graph.

From the diagram, it is clear that John is 5 ft tall is standing 20 feet away from a tree, making an angle of elevation to be 38⁰.

The diagram makes a right-angled triangle.

  • Given the angle = Ф = 38⁰
  • Adjacent = a = 5 ft
  • Opposite = b = 20 ft
  • Hypotenuse = Tree length = c  ?

Pythagorean Theorem:

For a right-angled triangle, with sides 'a' and 'b', the hypotenuse 'c' is defined as:

\:c=\sqrt{a^2+b^2}

substituting a=5, b=20

c=\sqrt{5^2+20^2}

c=5\sqrt{17}

c=20.6 ft

Thus, the tree is 20.6 ft tall.

3 0
3 years ago
Need help please !!Solve the inequality. Show your work please(:<br> 5y +16≤56
yan [13]
Hope this can help u

3 0
3 years ago
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The table below shows how much paint it takes to paint the walls of a house. A 2-column table with 4 rows. Column 1 is labeled P
algol [13]

Answer:

the answer is c,Yes, because the ratios for each input and output are equivalent.

Step-by-step explanation:

6 0
3 years ago
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