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arsen [322]
3 years ago
14

The radioactive isotope of lead, Pb-209, decays at a rate proportional to the amount present at time t and has a half-life of 3.

3 hours. If 1 gram of this isotope is present initially, how long will it take for 70% of the lead to decay? (Round your answer to two decimal places.)
Mathematics
1 answer:
Ksenya-84 [330]3 years ago
5 0

Answer:

5.73 hours

Step-by-step explanation:

70% decay means 30% remains

.3 = (1/2)^(t/3.3)

take the log of both sides

log.3 = t/3.3 * log1/2

Divide both sides by log 1/2

log.3 / log1/2 = t/3.3

use calculator

1.736965594166206 = t/3.3

multiply both sides by 3.3

5.73198646074848 = t

rounded

t = 5.73 hours

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Solve the system of equations using elimination. How many solutions does the system have?
Morgarella [4.7K]

Answer:

I hope it helps u

Step-by-step explanation:

Let's solve your system by elimination.

15j+12k=18;5j+4k=6

Multiply the second equation by -3, then add the equations together.

(15j+12k=18)

−3(5j+4k=6)

Becomes:

15j+12k=18

−15j−12k=−18

Add these equations to eliminate j:

0=0

Answer:

Infinitely many solutions

Note:  Please Brain-list it ok dear!

If u have any doubt you can ask ok

6 0
2 years ago
Find the value of the expression 3m^2+2p^2-15 when m =3 and p = 10
mylen [45]

3m {}^{2}  +  {2p}^{2}  - 15
m = 3
p = 10

3 \times 3 {}^{2}  + 2 \times  {10}^{2}  - 15 =
3 \times 9 + 2 \times 100 - 15 =
27 + 200 - 15 =
212

Hence, the answer is 212.



5 0
3 years ago
Solve for x. Show your work with proper statements and notation.
9966 [12]

Answer:

x = 26

Step-by-step explanation:

The sum of the angles around point O = 360°, thus

x + 3x + 256 = 360 , that is

4x + 256 = 360 ( subtract 256 from both sides )

4x = 104 ( divide both sides by 4 )

x = 26

4 0
3 years ago
There are 48 students in the 6th-grade band. If this represents 30% of the students in 6th grade, how many students are in the 6
Artemon [7]

Answer:

160

Step-by-step explanation:

had the question before

4 0
2 years ago
Read 2 more answers
Two factors of -48 have a difference of 19. The factor with a
sdas [7]

Answer:

13

Step-by-step explanation:

Given number = -48

Listing out the possible factors of -48 in pairs along with their difference:

Factors (F_1\times F_2)  Difference (F1-F2)   Difference (F_2-F_1)

-2\times 24                  -26                                  26

2\times -24                  26                                 -26

-3\times 16                   -19                                   19

3\times -16                   19                                  -19

-4\times 12                   -16                                   16

4\times -12                   16                                  -16

6\times -8                   -14                                   14

12\times -4                   14                                  -14

On listing out the factors we find out that two of the pairs have difference = 19

The pairs are -3, 16 and  3,-16

It is given that the factor with greater absolute value is positive. This means 16 would be positive while 3 would be negative.

So, our factors are -3, 16

The sum of the factors is = -3+16=13 (Answer)

3 0
3 years ago
Read 2 more answers
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