Why does 7.85 rounds up to 7.9?

The number 7.85 rounds up to 7.9 because when rounding to one decimal place, you look at the digit in the hundredths place, which is 5 in this case. According to rounding rules, if this digit is 5 or greater, you round up the tenths place by one. Therefore, 7.8 becomes 7.9 when rounding 7.85.