The error in rounding a number is half of the unit of measure. The number was rounded to the nearest 0.1 unit so the error is half of 0.1 which is 12⋅0.1=0.05
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⋅0.1=0.05. Since 3.7+0.05=3.753.7+0.05=3.75 and 3.7−0.05=3.653.7−0.05=3.65, then the error interval is \boxed{3.65\le x<3.75}.
