We must find UNIQUE combinations because choosing a,b,c,d... is the same as d,c,b,a...etc. For this type of problem you use the "n choose k" formula...
n!/(k!(n-k)!), n=total number of choices available, k=number of choices made..
In this case:
20!/(10!(20-10)!)
20!/(10!*10!)
184756
t = 5.3 years
(about 5 years 4 months)
Equation:
t = (1/r)(A/P - 1)
Calculation:
First, converting R percent to r a decimal
r = R/100 = 7.2%/100 = 0.072 per year,
then, solving our equation
t = (1/0.072)((4835.6/3500) - 1) = 5.3
t = 5.3 years
Answer:
A is true but I dont know the rest I am very sorry .-.
Step-by-step explanation:
I Just added 18 + 12 = 30 + 10 = 40 and that is why A is true
