Question

A laboratory has 20 grams of a radioactive substance that decays in such a way that t days later the number of grams left will be y = 20 (1/10)^(t/15). How many days does it take for half of the substance to decay?

Answer 1

@dumbcow

Answer 2

half of 20 is 10 .... set it equal to 10 and solve for "t"

Answer 3

remember
\[\ln (a^{t}) = t*\ln a\]

Answer 4

ok can you write out the equation for me i still dont get it much

Answer 5

\[20*(1/10)^{t/15} = 10\]
\[(1/10)^{t/15} = 1/2\]
take log of both sides

Answer 6

log(1/2)/ log 1/10 i got .30.....

Answer 7

yes .301

Answer 8

thn multiply 15 right

Answer 9

yep

Answer 10

4.5 Thanks :D

Answer 11

:)