If the half-life is t, then every t days, the amount of the radioactive isotope will be cut in half.
(1/2)^(number of half-lives) = 3%
number of half-lives = ln(0.03) / ln(0.5)
This gives the number of half-lives as 5.06.
Then 300 days = (5.06)(length of 1 half-life)
length of 1 half-life = 300 / 5.06 = 59.29 days
For any arbitrary 2x2 matrices
and
, only one choice of
exists to satisfy
, which is the identity matrix.
There is no other matrix that would work unless we place some more restrictions on
. One such restriction would be to ensure that
is not singular, or its determinant is non-zero. Then this matrix has an inverse, and taking
we'd get equality.
Answer: She had 200 cards to start with
Step-by-step explanation:
Let x = the amount of cards she had initially. This means she had x cards to start with.
She gave half of the cards she had to a friend. This means she gave her friend x/2 cards. She is left with with (x-x/2) = x/2 cards.
She also gave 1/4 of the remaining cards to her brother. This means that she gave (1/4 × x/2) = x/8 cards to her brother.
Remaining number of cards will be x/2 - x/8 = (4x-x)/8 = 3x/8
She still has 75 cards left. This means
3x/8 = 75
Cross multiplying with 8, it becomes
3x = 75×8 = 600
x = 600/3 = 200
She had 200 cards to start with.
