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vovangra [49]
3 years ago
13

The half-life of a radioactive isotope is the time it takes for a quantity of the isotope to be reduced to half its initial mass

. Starting with 220 grams of a radioactive isotope, how much will be left after 3 half-lives?
Mathematics
1 answer:
Sauron [17]3 years ago
6 0

Answer:

Quantity remaining= 27.5 grams

Step-by-step explanation:

If the initial quantity of the radioactive isotope= 220 grams

And for each half life it will reduce to half of its original quantity

For first half life

Quantity= 220/2

Quantity= 110 grams

Now for the second half life , the quantity to work with will be 110 grams

Second half life

Quantity= 110/2

Quantity= 55 grams

For the third half life , the quantity to work with is 55 grams

Third half life

Quantity= 55/2

Quantity= 27.5 grams

So after 3 half life's of this radioactive isotope, the amount remaining out of 220 = 27.5 grams.

Another simple way to do this

Since half life reduce the isotope by half of its original.

The third half life will reduce it by (1/2)^3= 1/8

So the quantity remaining= 1/8*220

Quantity remaining= 27.5 grams

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2. Circle C, has center (0,0) and radius 2.
adell [148]

Answer:

2. x ²  +  y ² =  4

3. x² + y² = 23

Step-by-step explanation:

The equation of a circle with center  

( a , b )  and radius  r  is:

( x − a )²   +  ( y − b ) ² =  r ²

Explanation:

Here,

 a = 0 ,  b = 0 ,  r = 2  

The equation is:

( x -0 ) ² +  ( y -0 ) ² =  ( 2  ) ²

that is:  x ²  +  y ² =  4  

Thus:

x ²  +  y ² =  4

3. Each point on a circle has the same distance from the center. This distance is the radius  r  of the circle.

 Here, ( -3 , 4 )  is a point on the circle, meaning that the radius of the circle is the distance between  ( 0 , 0 ) , the center, and  ( -3 , 4 ) .

thus  a circle centered on the origin will have an equation of:

x² + y² =r²

And,  ( -3 , 4 )  lies on the circle, we have:

(-3)² + (4)² = r²

9 + 14 = 23

substituting;

x² + y² = 23

8 0
3 years ago
Assume you are planning a picnic for lunch, but when you woke up there were rain clouds in the sky. If 50% of rainy days start w
Tasya [4]

Answer:

0.25 = 25% probability that it will rain today and ruin your picnic

Step-by-step explanation:

Conditional Probability

We use the conditional probability formula to solve this question. It is

P(B|A) = \frac{P(A \cap B)}{P(A)}

In which

P(B|A) is the probability of event B happening, given that A happened.

P(A \cap B) is the probability of both A and B happening.

P(A) is the probability of A happening.

In this question:

Event A: Cloudy skies

Event B: Rain

20% of all days start with clouds in the air

This means that P(A) = 0.2

50% of rainy days start with rain clouds in the air

50% of 10%. So

P(A \cap B) = 0.5*0.1 = 0.05

What is the probability that it will rain today and ruin your picnic

P(B|A) = \frac{P(A \cap B)}{P(A)} = \frac{0.05}{0.2} = 0.25

0.25 = 25% probability that it will rain today and ruin your picnic

3 0
3 years ago
Solve the following: 2(6x + 5) = 94
Black_prince [1.1K]

Answer: x=7

Step-by-step explanation:

Step 1: Simplify both sides of the equation.

2(6x+5)=94

(2)(6x)+(2)(5)=94(Distribute)

12x+10=94

Step 2: Subtract 10 from both sides.

12x+10−10=94−10

12x=84

Step 3: Divide both sides by 12.

12x

12

=

84

12

x=7

6 0
3 years ago
Read 2 more answers
On a rectangle hyperbola, if one point is (2,3) and y varies inversely to x, find y when x is 6
s344n2d4d5 [400]
<span>The graph of y against x in inverse proportion is a rectangular hyperbola but I don't see at all how this knowledge/observation is any help in solving the problem.

Inverse proportion means that as x doubles y will halve and the equation is xy = k where k is some number. A good example of inverse proportion is speed and time taken over some fixed distance. In this case x could represent the speed (mph) and y the time (h) and then k is the distance in miles.

Since we know y=3 when x=2 we have xy = 6. Now it's easy to see when x=6 y=1.</span>
4 0
3 years ago
What is the value of 5 in 756 write and draw to explain how you know?
kykrilka [37]

In the attached diagram you can see Place Value Chart that is used to help understand the value of each digit based on the place or position.

For the number 756:

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  • 6 has a value of 6 ones, or 6.

Answer: 5 has a value of 5 tens, or 50

8 0
3 years ago
Read 2 more answers
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