Via half-life equation we have:

Where the initial amount is 50 grams, half-life is 4 minutes, and time elapsed is 12 minutes. By plugging those values in we get:

There is 6.25 grams left of Ra-229 after 12 minutes.
One way is speed=distance divided by time
yes she is very safe inside
Answer:
33.61°
Explanation:
Refractive index is equal to velocity of the light 'c' in empty space divided by the velocity 'v' in the substance.
Or ,
n = c/v.
v is the velocity in the medium (2.3 × 10⁸ m/s)
c is the speed of light in air = 3.0 × 10⁸ m/s
So,
n = 3.0 × 10⁸ / 2.3 × 10⁸
n = 1.31
Using Snell's law as:
Where,
is the angle of incidence ( 25.0° )
is the angle of refraction ( ? )
is the refractive index of the refraction medium (air, n=1)
is the refractive index of the incidence medium (glass, n=1.31)
Hence,
Angle of refraction =
= 33.61°
Independent- nose of the airplane
dependent - paper clips
control - how many paper clips