In maths, the term "lower bound" refers to the smallest value that a rounded number could actually be. Think of it like a minimum limit or floor that the number can’t go below.
For example, you may have a number that has been rounded to one decimal place as 6.5. The lower bound is 6.45, because 6.45 would be rounded up to 6.5, but a smaller number like 6.44 would be rounded down to 6.4. Or for something that is measured as 8 cm to the nearest centimetre, the lower bound would be 7.5 cm because 7.5 cm would be rounded up to 8 cm, but a smaller value like 7.4 cm would be rounded down to 7 cm.
Lower bounds are important when you are working on questions about estimating measurements, as they help you understand the smallest possible value something can be. In your GCSE Maths course, you'll often use lower bounds to help solve problems and make sure your answers are accurate.
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