The decimal place to the right of the tenths place is the hundredths place. The digit in that place is 9.
When the digit to the right of the place you're rounding to is more than 4, you increase the digit in the rounding place by 1.
Here, we have the hundredths digit is 9, which is more than 4, so we increase the tenths digit by 1. The rounded number is
... 56.4
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Another way to get there is to add 5 in the hundredths place (the place to the right of the one you're rounding to). When you do that, you get 56.448. Now, throw away all the digits to the right of the one you're rounding to. This leaves
... 56.4
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The reason I show this last method is to deal with cases like rounding 56.978. By the first rule, you're increasing the digit 9 by 1, which might be confusing. (it requires a carry into the next digit, making 57.0.) If you add .05 to this number, you get 56.978 +.05 = 57.028. Now when you throw away the digits to the right of the tenths digit, you have 57.0.
