Converting decimals to fractions and a word problem on interest rate

Hello!

I have two questions.

1) Convert 1.2(with the 2 as a recurring number) into a fraction.

My book instructs to multiply the decimal number by ten if there is only one recurring number so

x= 0.12

10x: 1.2

Then the book instructs me to subtract 0.12 from 1.2 .

Then 9X= 1.08

and the fraction for this decimal is 1.08/9.

Am I correct?

2)

Can someone please help me with this word problem?

Jessica invests 10 000 €. In four years her investment has grown to 10 800€.

What is the interest rate?

Thank you!