The formula for half-life is:

$A = P(0.5)^{t/h}$

A is the amount remaining, P is the initial amount, t is the time that has passed, and h is the half-life of the substance. Plug in the values that you know and solve:

$4 = P(0.5)^{35/20} \\ \\ 4 = P(0.5)^{1.75} \\ \\ P = \frac{4}{0.5^{1.75}} \\ \\ P \approx 13.4543426441$

Rounded to the nearest whole number, the density of the substance was about 13<span>mg / cm².</span>

8 0

3 years ago

In a sample with mean x = 12 and standard deviation s = 3.5, a data point at 16.8 would have what sample z-score?

sammy [17]

$\dfrac{16.8-12}{3.5}\approx1.37$

3 0

3 years ago

When you add a positive and negative number, how can you tell whether the sum will be positive or Negative?

Lera25 [3.4K]

Answer:

just remember this:

negative x negative = positive

positive x positive = positive

postive x negative = negative

negative x postive= negative

lookon bbcbitesize for adding negatives and positive rule

8 0

3 years ago