Answer:
2.6 billion years
Explanation:
There are essentially two ways of solving nuclear half-life problems. One way is by applying the half-life formula, which is
A
(
t
)
=
A
0
(
t
)
⋅
(
1
2
)
t
t
1
2
, where
A
(
t
)
- the quantity that remains and has not yet decayed after a time t;
A
0
(
t
)
- the initial quantity of the substance that will decay;
t
1
2
- the half-life of the decaying quantity;
In this case, the rock contains
1/4th
of the orignal amount of potassium-40, which means
A
(
t
)
will be equal to
A
0
(
t
)
4
. Plug this into the equation above and you'll get
A
0
(
t
)
4
=
A
0
(
t
)
⋅
(
1
2
)
t
t
1
2
, or
1
4
=
(
1
2
)
t
t
1
2
This means that
t
t
1
2
=
2
, since
1
4
=
(
1
2
)
2
.
Therefore,
t
=
2
⋅
t
1
2
=
2
⋅
1.3 = 2.6 billion years
A quicker way to solve this problem is by recognizing that the initial amount of the substance you have is halved with the passing of each half-life, or
t
1
2
.
This means that you'll get
A
=
A
0
2
after the first 1.3 billion years
A
=
A
0
4
after another 1.3 billion years, or
2
⋅
1.3 billion
A
=
A
0
8
after another 1.3 billion years, or
2
⋅
(
2
⋅
1.3 billion
)
During hibernation, the animals don't eat anything.....So, when they are hibernating, those animals can get energy by burning the the stored fat from the fatty food and can survive until they wake from hibernation
Explanation:
Meiosis I
At the beginning of meiosis I, a human cell contains 46 chromosomes, or 92 chromatids (the same number as during mitosis). Meiosis I proceeds through the following phases:
■ Prophase I: Prophase I is similar in some ways to prophase in mitosis.