To estimate a decimal to the tenths place, you have to round the number from the hundredths place. It all depends on the hundredths place to round a decimal to the tenths place. Let's say that you have a math problem and the answer is 10.46574658, but it says to round to the tenths place. So, you take the first four numbers from the answer, which would be 10.46, go to the tenths and the hundredths. If the number in the hundredths place is greater than 5, round the tenths number up. If the number in the hundredths place is less than 5, it stays the same. So with the number 10.46, the number in the hundredths place is greater than 5, so you round the number in the tenths place up, which becomes 10.5.
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