7978 years
Step-by-step explanation:
A = A02^(-t/hl)
where hl = half-life.
Dividing both sides by A0 and taking the logarithm, we get
ln(A/A0) = -(t/hl)ln2
or solving for t,
t= -(hl)ln(A/A0)/ln2
note that A/A0 = 0.38
t = -(5715 yrs)[ln(0.38)/ln2]
= 7978 years
The two numbers are 41 & 37.
The way to solve this is by setting up an equation. We know that 2 numbers are going to equal 78, so here would be the general equation (let x represent the number we don't know):
(x) + (x + 4) = 78
Now, we need to simplify it (combine like terms):
2x + 4 = 78
Then you can solve it like any other equation. Subtract 4 on both sides:
2x = 74
Divide by 2 on both sides:
x = 37.
So, now you know one number is equal to 37 and that the other is 37 + 4.
That's how you get 37 & 41.
