PLS HELP< FIRST TO ANSWER GETS BRANLIEST AND 14 POINTS PLSS EMERGENCY
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Answer:
A) 277 million years
Step-by-step explanation:
Here, decay of U-238 is first order reaction. (since most of the nuclear decays are first order).
so, the equation t = × ln(
)
where, t = time from start of reaction
k = reaction constant
A(0) = initial concentration; A = present concentration.
⇒ 4.5 billion = 4500 million years = × ln2.
Now, given 95.82% of parent U-238 isotope is left.
⇒ t = × ln(
)
t = × ln(
)
⇒ t ≅ 277 million years.
Answer:
The value of a is 10.
Step-by-step explanation:
We are given with the following pair of the linear system of equations below;
and
.
Also, the solution is given as (a, -1).
To find the value of 'a', we have to substitute the solution in the equation because it is stated that (a, -1) is the solution of the given two equations.
So, the x coordinate value of the solution is a and the y coordinate value of the solution is (-1).
First, taking the equation;
Put the value of x = a and y = -1;
(-1) = -(a) + 9
a = 9 + 1 = 10
Now, taking the second equation;
Put the value of x = a and y = -1;
0.5a = 6 - 1
0.5a = 5
a = 10
Since we get the value of a = 10 from the equations, so the value of a is 10.