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3 years ago

How do I work this -(-3)-[-(-4]-2+7

Mathematics

1 answer:

OLga [1]3 years ago

4 0

Answer:

Step-by-step explanation:

-(-3)-[-(-4)]-2+7 = 3 - [4] - 2 + 7 = 3 - 4 - 2 + 7 = (3+7) - (4+2) = 10 - 6 = 4

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3/7 - 10/7 Write fractions in simplest form

8_murik_8 [283]

<span>3/7 - 10/7
= - 7/7
= -1

answer
-1</span>

3 0

3 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

3 years ago

Anna is planning a big birthday bash for her sixteenth birthday party and wants to invite as many people as possible but she has

Hitman42 [59]

P=(500-100)÷6.50
p=400÷6.50
p=6.15

7 0

3 years ago

Read 2 more answers

<img src="https://tex.z-dn.net/?f=%28%5Cfrac%7Bz%7D%7B4%7D%20%2B30%29%20%2B%20%28%5Cfrac%7Bz%7D%7B2%7D%20%29%20%3D%20180" id="Te

Dovator [93]

Answer:

x = 200

Step-by-step explanation:

Multiply by 4:

x + 120 + 2x = 720

3x = 600 . . . . . . collect terms, subtract 120

x = 200 . . . . . . . divide by 3

_____

<em>Check</em>

(200/4 +30) +(200/2) = 180

(50 +30) + 100 = 180

80 + 100 = 180 . . . . . true

_____ _____

<em>Alternate solution</em>

If you like, you can simply work with the equation given.

(3/4)x + 30 = 180 . . . . collect terms

(3/4)x = 150 . . . . . . . . . subtract 30

x = 200 . . . . . . . . . . . . multiply by 4/3

4 0

3 years ago

Please i need help thank you!..

Mamont248 [21]

Question 4 is Choice A
Question 5 is Choice B
Question 6 is Choice C
Question 7 is Choice B

These are relatively simple it’s just understanding the relations of x and y values :)

3 0

3 years ago