The answer depends on 6.5 WHAT! Seconds? Millennia?
A decade is ten years. Therefore, 6.5 is 65 years.
65 years
65 because 1 decade = 10 years
6.5 decades is equivalent to 65 years
100 decades in a millennium
16.7 decades
There are 20 decades.
1.2 decades
fifty decades
70 decades
How many months are in 4 decades
There are 3.5 decades in 35 years