Caffeine is the active ingredient in coffee and many energy drinks. once caffeine is consumed it
has a half-life in the body of approximately 4 hours. an average cup of coffee contains 100mg of
caffeine. suppose you drink a cup of coffee at 8am, followed by another cup at 10am and an
afternoon cup of coffee at 3pm. how much caffeine is left in your body when you go to sleep at
11pm?

1 half-life = 4 hours

8 AM = 100 mg

(2 hours)

10 AM = 50 + 100 mg

(4 hours)

3 PM = 25 + 100 mg

(8 hours)

11 PM = --> 0 mg <--

second option

step-by-step explanation:

the measures of a triangle equal 180. use that to find x.

2x+3x+4x=180

9x=180

9x/9=180/9

x=20

now you know x, you know angle a is 40°, angle b is 60°, angle c is 80°.

because angle a is 40°, the first option doesn't work.

because angle b is 60°, the second option does work.

when you add angle a and b, you get 100°. complementary means it equals 90°, so the third option doesn't work.

when you add angle a and c, you get 120°, which is not 100.