You write it like this
2.90
Ninety hundredths as a decimal is 0.90
Ninety-seven hundredths.
five and ninety hundredths
0.99
Six and ninety-nine hundredths
Nine and ninety-four hundredths.
Ninety-four hundredths.
Ninety-five and ninety-seven hundredths.
Ninety-five hundredths.
0.92
99,000,000.02 is 9.900000002 x107
Four and ninety-one hundredths.