The answer is 3.4.
3.447
^tenths place
Rounding it to one decimal place is rounding it to the nearest tenth. Look at the number to the right of the tenths place(hundredths place). If it's 5 or more we round up to 3.5, if it's 4 or less we round down to 3.4.
3.447
^number in hundredths place is 4
So we round 3.447 to 3.4.