There is a common ratio of 2/3 between the height of the ball at each bounce. So, the bounce heights form a geometric sequence: 27, 18, 12. Two-thirds of 12 is 8, so on the fourth bounce, the ball will reach a height of 8 feet.
we have
x ----> number of hats the sold
y ----> number of scarves they sold
so
12x+15y=690 ------> equation A
y=x+10 -----> equation B
Solve the system of equations
Using substitution Method
substitute equation B in equation A
12x+15(x+10)=690
solve for x
12x+15x+150=690
27x=690-150
27x=540
x=20
Find out the value of y
y=x+10
y=20+10
y=30
therefore
The answer is
<h2>20 hats and 30 scarves</h2>
Initial amount, 
.
Final amount, 
.
Time taken, t = 6:00 - 2:00 = 4 hour.
We know,
Therefore, the half-life of the isotope is 1.024 hours.
Hence, this is the required solution.
The equation for this will be y=3/8x+7.
