Answer:
[7.25, 7.35)
Explanation:
The least significant digit is in the tenths place. The error can be as much as half of one tenth, or 0.05.
The lower bound is ...
7.3 - 0.05 = 7.25 . . . . . error subtracted from value
The upper bound is ...
7.3 + 0.05 = 7.35 . . . . . error added to value
Since 7.35 is rounded up to 7.4, the maximum value of L must be less than that.
7.25 ≤ L < 7.35 . . . meters
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In many cases, the upper bound on L is taken to be exactly 7.35. For all practical purposes it is. If you're asked for upper and lower limits, you'd have to say they are 7.35 and 7.25 m, respectively.