We want to select 3 pairs of people from a group of 6.
We use the formula:
n! / (r! * (n -r)!)
where n = 6 and r = 2
combinations = 6! / (2! * 4!) =
combinations = 6 * 5 / 2
combinations = 15
Source:
1728.com/combinat.htm
Answer:
5
Step-by-step explanation:
Interest would be $15 every 3 years
Interest = Principal x Rate x Time
Interest = 100 x 5% x 3
Interest = 5 x 3
Interest = 15
170years
R/100=2.5%
time= 100=0.025 per year (1/0.025) (5200\1000)-1=168
time=168 years