Answer
Part 1: Three and four tenths.
Part 2: 3.0 + 0.4
Explanation.
When writing numbers in words we must use the concept of place values. In this case for instance, the place value of 3 is ones and the place value of 4 is tenths hence called the "four tenths".
3.4 can be written as the sum of 3 and 0.4. So 3.4 in its expanded form is (3+0.4).
