Suppose an unknown radioactive substance produces 12800 counts per minute on a geiger counter at a certain time, and only 800 counts per minute 10 days later. assuming that the amount of radioactive substance is proportional to the number of counts per minute, determine the half-life of the radioactive substance.

2.5 days.

Step-by-step explanation:

The number of half lives  is n where

12800(0.5)^n = 800

12800(0.5)^4 = 800

so n = 4

So the half life is 10/4

= 2.5 days.

54

step-by-step explanation:

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

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