The half-life of a certain radioactive substance is 65 days. there are 3.5 g present initially.
a. express the amount of substance remaining as a function of time t.
b. when will there be less than 1 g remaining?

r = 3.5 * .5^(t/65); around 117.5 days

Step-by-step explanation:

r = remaining substance

t = time in days

The half life is 65 day, meaning the .5 must be put to a power of t/65.

The initial substance was 3.5, which we must substitute in.

After using logarithms to solve our new equation, we are left with t=(about)117.5 days for there to be less than 1 gram of substance remaining.

to find the perimeter of the rectangle this is the expression:

x-9+x-9+3x-4+3x-4=138

if we simplify it:

8x-26=138

remember, 138 is what it all adds up to

the length is 11.5cm

the width is 57.5cm

the area is 661.25cm^2

the answers might not be correct use at own risk