compound interest equation for annually compounded

A=final amount
P=principal
r=rate in decimal
t=time in years
given that
A=1550
P=1000
r=5.5%=0.055
find t

divide both sides by 1000

take ln of both sides

use ln rule 

divide both sides by ln(1.055)

using a calculator, we get that t=8.18544 yrs
so about 8.2yrs
Your answer would be 5.10... Hope this helps :)
Answer:
56in3
Step-by-step explanation:
Answer: 21 questions
Step-by-step explanation:
Turn it into a number sentence.
72% of x amount of questions is 15
0.72(x) = 15. Divide both sides by 0.72
x= 20.83333 round to nearest whole number
x= 21 questions