3.9
It is a decimal fraction.
They are dense in that between any two decimals you have another one. A much better way to think of it is that a decimal must be either rational or irrational. For example, .34 is certainly rational, but the decimal expansion of square root of 2 goes on forever and is irrational. So a decimal, being either one, must be dense in the reals.
A "Light year" is a distance. It's the distance light travels in one year, in vacuum.5,878,450,000,000 miles (rounded)9,460,450,000,000 kilometers (rounded)
Double it, divide by one hundred. 0.86
It is already rounded to exactly that degree.
49.72 rounded to one decimal place is 49.7.
It is 44.3 when rounded to one decimal place
It is then 5.7 when rounded to one decimal place
978.229 rounded to one decimal place is 978.2
It is 0.5 when rounded to one decimal place.
3.48 rounded to one decimal place is 3.5.
3.05 rounded to one decimal place is 3.1.
44.98 rounded to one decimal place is 45.0
13.3131 rounded to one decimal place = 13.3
2.91 rounded to one decimal place is 2.9
1.13 rounded to one decimal place is 1.1