Question

insert 16 rational number between 2.1 and 2.2

Answer 1

You can insert any rational number between any 2 numbers by this formula
$\frac{a + b}{2}$
So at first,

2.1+2.2 /2 = 4.3/2 = 2.15

then take 2.1 and 2.15

2.1+2.15 /2 = 2.125

and so on and just like this, you will get 16 or more rational numbers between 2.1 and 2.2.