50 is decreased to 19. what is the percent of change?

nlexa [21]

-16 + (-8) = -24
(-4) - 7 = -11
-24 - (-9) = -15
6.25 + (-8.50) = 2.25
10.8 - (6.4) = 4.4
-54.26 + (-15.42) = -69.68

F ur fractions

6 0

2 years ago

Suppose after 2500 years an initial amount of 1000 grams of a radioactive substance has decayed to 75 grams. What is the half-li

krok68 [10]

Answer:

The correct answer is:

Between 600 and 700 years (B)

Step-by-step explanation:

At a constant decay rate, the half-life of a radioactive substance is the time taken for the substance to decay to half of its original mass. The formula for radioactive exponential decay is given by:

$A(t) = A_0 e^{(kt)}\\where:\\A(t) = Amount\ left\ at\ time\ (t) = 75\ grams\\A_0 = initial\ amount = 1000\ grams\\k = decay\ constant\\t = time\ of\ decay = 2500\ years$

First, let us calculate the decay constant (k)

$75 = 1000 e^{(k2500)}\\dividing\ both\ sides\ by\ 1000\\0.075 = e^{(2500k)}\\taking\ natural\ logarithm\ of\ both\ sides\\In 0.075 = In (e^{2500k})\\In 0.075 = 2500k\\k = \frac{In0.075}{2500}\\ k = \frac{-2.5903}{2500} \\k = - 0.001036$

Next, let us calculate the half-life as follows:

$\frac{1}{2} A_0 = A_0 e^{(-0.001036t)}\\Dividing\ both\ sides\ by\ A_0\\ \frac{1}{2} = e^{-0.001036t}\\taking\ natural\ logarithm\ of\ both\ sides\\In(0.5) = In (e^{-0.001036t})\\-0.6931 = -0.001036t\\t = \frac{-0.6931}{-0.001036} \\t = 669.02 years\\\therefore t\frac{1}{2} \approx 669\ years$

Therefore the half-life is between 600 and 700 years

5 0

2 years ago

A math teacher keeps her wall-sized graph paper in a box shaped like a triangular prism. The triangular face of the prism has a

yaroslaw [1]

(24 × 17 × 130\2)

24 × 17 = 408 x 130 = 53,040 / 2 = 26,520
So the volume of this box is

C= 26,520 cm^3

6 0

1 year ago

Easyy I need help guys...(easy fractions)

Ivanshal [37]

1a. 5/10 can be simplified to 1/2. (5 divided by 5 is one, 10 divided by 5 is 2.)

1b. 9/12 can be simplified to 3/4. (9 divided by 3 is 3, 12 divided by 3 is 4.)

1c. 12/18 can be simplified to 2/3. (12 divided by 6 is 2, 18 divided by 6 is 3.)

1d. 9/24 can be simplified to 3/8. (9 divided by 3 is 3, 24 divided by 3 is 8.)

1e. 27/90 can be simplified to 3/10. (27 divided by 9 is 3, 90 divided by 9 is 10.)

1f. 40/48 can be simplified to 5/6. (40 divided by 8 is 5, 48 divided by 8 is 6.)

8 0

2 years ago

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The fire department needs to rescue a man from a house. There is a large, unstable puddle below the house. The ladder needs to b

nevsk [136]

Answer: 100 feet

Step-by-step explanation:

60+40=100

5 0

2 years ago

Read 2 more answers