Question

Can someone tell me if this is correct?
The half-life of a radioactive isotope is the time it takes for a quantity of the isotope to be reduced to half its initial mass. Starting with 215 grams of a radioactive isotope, how much will be left after 4 half-lives?Use the calculator provided and round your answer to the nearest gram.

f=215(1+0.005)^4=219.33235763
so would it be 219.32?

Answer 1

@phi can you see if I got this right?

Answer 2

The half-life of a radioactive isotope is the time it takes for a quantity of the isotope to be reduced to half its initial mass

that means if you start with 100, after one half-life, you will have 50
your answer should be smaller than the amount you start with.

Answer 3

Got a little confused there but would it be 210

Answer 4

where did you get your formula?

I would use
215*(0.5)^n
where n is the number of half-lifes

Answer 5

i got it from the explain tab it says to use those formulas so would it be 13.4375

Answer 6

yes, that looks better
you could do it like this
215 --> 107.5 (1 half life)
107.5/2 = 53.75 (2nd)
53.75/2 = 26.875 (3rd)
26.875/2= 13.4375 (4 half lifes)

the formula is faster to use.

Answer 7

but it said to the nearest gram so would it be 13.42?

Answer 8

the starting amount is in grams so the answer 13.4375 is in grams

round to the nearest gram means the nearest whole number

you have 13.4 (plus a tiny bit more)
is 13.4 closer to 13 or to 14 ?

Answer 9

13

Answer 10

so the answer would be 13?

Answer 11

yes 13

the rule in rounding is look at the next lower digit
13.4 <-- look at the 4
if 5 or bigger round up (to 14)
else round down to 13

Answer 12

Thank you mind helping me with another one ?Once I get it solved since this is my last question.