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sergiy2304 [10]
2 years ago
5

The half-life of radium is 1690 years. If 80 grams are present now, how much will be present in 870 years?

Mathematics
1 answer:
almond37 [142]2 years ago
5 0

Answer:

A(t) = amount remaining in t years

= A0ekt, where A0 is the initial amount and k is a constant to be determined.

Since A(1690) = (1/2)A0 and A0 = 80,

we have 40 = 80e1690k

1/2 = e1690k

ln(1/2) = 1690k

k = -0.0004

So, A(t) = 80e-0.0004t

Therefore, A(430) = 80e-0.0004(430)

= 80e-0.172

≈ 67.4 g

Step-by-step explanation:

hope it helpful for you ❤️

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In one school, half of all students who like math like science as well. Also, in that school, a third of all students who like s
Nimfa-mama [501]

Answer:

2/3

Step-by-step explanation:

If we have 'x' students who like math and 'y' students that like science, we can formulate that:

Half of x likes math and science, and also one third of y likes math and science, so:

(1/2) * x = (1/3) * y

x / y = (1/3) / (1/2)

x / y = (1/3) * 2 = 2/3

So the ratio of the number of students who like math to the number of students who like science is 2/3

3 0
3 years ago
Read 2 more answers
A metallic sphere is immersed in water in a cylindrical container causing a rise in the level of water by 7.5cm if the cylinder
SVETLANKA909090 [29]

Answer:

6.51 cm

Step-by-step explanation:

Since the sphere causes the water level in the cylindrical container to rise and thus increase by its own volume, the volume of the sphere is V = 4πr³/3 where r = radius of sphere. The volume rise of the container is thus    V' = πR²h where R = radius of base of cylinder = 7 cm and h = height of water level = 7.5 cm.

Since V = V',

4πr³/3 = πR²h

dividing through by π, we have

4r³/3 = R²h

multiplying both sides by 3/4, we have

r³ = 3R²h/4

taking cube-root of both sides, we have

r = ∛(3R²h/4)

Substituting the values of the variables into the equation, we have

r = ∛(3(7 cm)² × 7.5 cm/4)

r = ∛(3 × 49 cm² × 7.5 cm/4)

r = ∛(1102.5cm³/4)

r = ∛(275.625 cm³)

r = 6.508 cm

r ≅ 6.51 cm to 2 decimal places

3 0
2 years ago
When will the equation p(b)=520(0.88)^b have a value less than 100?
yulyashka [42]

Answer:

The given equation will have value less than 100 whenever the value of b is greater than 12.89

Step-by-step explanation:

For the given equation, p(b) = 520 × 0.88^{b} to have a value less than 100 we can establish inequality as:

                     p(b) < 100

         or,  520 × 0.88^{b} < 100

         or, \frac{520}{520} × 0.88^{b} < \frac{100}{520}

         or, 0.88^{b} < \frac{1}{5.2}

         or, ㏒ ( 0.88^{b} ) < ㏒  (\frac{1}{5.2})

         or, b× ㏒ 0.88 < ㏒  (\frac{1}{5.2})

         or,  \frac{log (\frac{1}{5.2}) }{log (0.88)}   <  b

         or, 12.89 < b

Hence for the equation to have value less than 100, b must be greater than 12.89.

3 0
3 years ago
Add an intersection the red light times normally distributed by the mean of three minutes and a standard deviation of .25 minute
Soloha48 [4]

95% of red lights last between 2.5 and 3.5 minutes.

<u>Step-by-step explanation:</u>

In this case,

  • The mean M is 3 and
  • The standard deviation SD is given as 0.25

Assume the bell shaped graph of normal distribution,

The center of the graph is mean which is 3 minutes.

We move one space to the right side of mean ⇒ M + SD

⇒ 3+0.25 = 3.25 minutes.

Again we move one more space to the right of mean ⇒ M + 2SD

⇒ 3 + (0.25×2) = 3.5 minutes.

Similarly,

Move one space to the left side of mean ⇒ M - SD

⇒ 3-0.25 = 2.75 minutes.

Again we move one more space to the left of mean ⇒ M - 2SD

⇒ 3 - (0.25×2) =2.5 minutes.

The questions asks to approximately what percent of red lights last between 2.5 and 3.5 minutes.

Notice 2.5 and 3.5 fall within 2 standard deviations, and that 95% of the data is within 2 standard deviations. (Refer to bell-shaped graph)

Therefore, the percent of  red lights that last between 2.5 and 3.5 minutes is 95%

8 0
3 years ago
The width of a rectangle is the length minus 2 units. the area of the rectangle is 35 units
Mariana [72]

Answer:

Length=7units\\\\Width=5units

Step-by-step explanation:

Width=(Length-2) units

W=(L-2) units

Area of the rectangle= 35 square units

Area = length* Width

35= L*(L-2)\\\\35=L^2-2L

Subtracting 35 both sides:

L^2-2L-35=0

Solving the quadratic equation for 'L' ;

Using factorization:

L^2+5L-7L-35=0

Taking common from the equation :

L(L+5)-7(L+5)=0\\\\(L+5)(L-7)=0\\\\L+5=0\\\\L=-5

OR

L-7=0\\\\L=7

The length cannot be negative, therefore Length(L)= 7

Width=Length-2\\\\=7-2\\\\=5 units

Length=7units\\\\Width=5units

8 0
3 years ago
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