Aresearcher measures 200 counts per minute coming from a radioactive source at noon. at 3: 00pm, she finds that this has dropped to 25 counts per minute. what percentage of the original source will remain at 6: 00pm?

1.5% will remain at 6.00pm.

Step-by-step explanation:

The function for exponential decay is,

where,

y(t) = the future amount,

A = initial amount,

r = rate of growth,

t = time.

A researcher measures 200 counts per minute coming from a radioactive source at noon.

At 3:00pm, i.e after 3 hours,she finds that this has dropped to 25 counts per minute.

Putting the values,

-ve sign means the amount is decreasing.

As we have to find the amount at 6.00pm i.e after 6 hours, so

As number of bacteria can't be in decimal.

So the percentage will be,