An element with mass 820 grams decays by 26.8% per minute. how much of the element is remaining after 18 minutes, to the nearest 10th of a gram?

3.0 grams of the element are left after 18 minutes

Step-by-step explanation:

Recall that an exponential decay that can be studied with the following formula for the amount of material (A) as a function of time (t):

where:

is the starting amount of the substance (in our case 820 grams)

r is the rate of decay (which in our case given as 26.8% can be written in decimal form as 0.268

and t is the time in minutes (in our case t = 18 minutes)

Then we have:

which can be rounded to 3.0 grams

c.

step-by-step explanation:

she should of added 9^2 and 12^2. that is because it is a^2+b^2=c^2. c^2 is the hypotenuse and should always be bigger than the other two numbers. which is why she should of added 9 squared and 12 squared together instead of 15 squared.