You can have a calculator add these numbers for you. Most will report the result as a decimal. There are fraction calculators on-line, if your graphing calculator does not have a fraction display mode.
If you want minutes, multiply the fraction (or decimal) by 60 minutes.
Because 4.7 is the "abbreviation" for 4.70 also 4.7 is the simplified version of 4.70 kind of like a fraction you 4 70/100 simplified is 4 7/10 or 4.7.