Radon-219 has a half-life of about 4 s. After 20 s, how many milligrams of a 500 mg sample will remain?

435.3 mg

211.6 mg

31.3 mg

15.6 mg

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15.6 mg

Step-by-step explanation:

First 4 s- 500/2= 250 mg

After 8 s- 250/2= 125 mg

After 12 s- 125/2= 62.5 mg

After 16 s- 62.5/2= 31.25 mg

At 20 s- 31.25/2= 15.625 mg

x = 2

step-by-step explanation:

if sr parallel to ba then the sides bc and ac are in proportion, that is

= ← substitute values

= ( cross- multiply )

27x = 6(4x + 1)

27x = 24x + 6 ( subtract 24x from both sides )

3x = 6 ( divide both sides by 3 )

x = 2