<span>Compound
interest formula</span>

Where
<span>
A= Future value
P =
the Principal (the initial amount of money)
r = annual interest rate</span>
t = time
<span>n=
number of times compounded in one t
Remark
----------------------------------------------------------------------------------
r is generally a percentage like 3%, 7% etc and
are applied in the formula as 0.03, 0.07...,
the interest is compounded generally annually (
n=1), quarterly (
n=4),
monthly (
n=12), etc...
t is in years,
In our problem:
</span>
A= 30 000
P =20 000
r = 15%=0.15
time = t = ?
n= 4
applying the formula:



75% of 12 months is 3/4 of 12 months, which is 9 months
Answer: 2 years, 9 months
8 rock in 5 minutes
54 rocks / 8 rocks = 6.75
6.75 x 5 minutes = 33.75 minutes
Let the first angle be x and the second be y.
Supplementary angles add up to 180, so:
x + y = 180
Also, as given in the statement:
x = 4y - 25
Substituting into the first equation:
4y - 25 + y = 180
5y = 205
y = 41
x = 4(41) - 25
x = 139
One angle is 139° and the other is 41°.
The answer is 7.75. Since there can not be 7.75 days, you can round that to 8 and say that it's almost 8 days. Hope this helps!
Supplementary angles add to 180
4+5=9
180/9=20
4*20=80
5*20=100
the angles are 80 degrees and 100 degrees