<span>half-life means you divide by 2
21.6 / 3.6 = 6 hf (hf = half-life)
then you divide by 2^6
6.02 x 10^23 / 2^6 = 9.40625 x 10^21 atoms
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26
3hf ===> 2^3
10.0 / 2^3 = 1.25 gram (remaining)
answer : 10 - 1.25 = 8.75g
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27
128 / 2^n = 2
64 = 2^n
n = 6
24 /6 = 4
4 days is the half-live of the sample
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28
2.5/4.46 of 50% initial mass
(2.5/4.46) x 0.5 x 2 = 0.5605 g
answer: 2 - 0.5605 = 1.4395 g
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29
2^7 = 128
so 7 half-lifes
7* 8040 = 56200 days
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30
the time of 10 half-lifes
= 10 x 0.334s = 3.34s </span><span>
</span>
7y - 2y + 8 = 19 + 4y
7y - 2y - 4y = 19 - 8
1y = 19 - 8
1y = 11
Ans is y = 11
Price + tax
650 + 5/100 x 650
650 + 32,5
= $682,5
I think your answer would be B
X - y + x + y = 180
2x = 180
x = 90
2x - 2y = x + y
x = 3y
y = x/3
y = 90/3
y = 30
x - y = 90 - 30 = 60
x + y = 90 + 30 = 120
2x - 2y = 180 - 60 = 120