# Upper and Lower Bounds

how to find and use the upper and lower bounds of numbers

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• Created by: Kelly:)
• Created on: 30-05-11 16:28

## Finding an Upper/Lower Bound

if you're given a question about upper/lower bounds in your exam, it will say something like 125 to the nearest metre. this means there's a difference of a metre between the upper and lower bound so in this case:

• upper bound = 125.5
• lower bound = 124.5

Don't worry about using 125.499999 (and so on) because your calculator will give you the same answer for this and 125.5

so if they say find the upper and lower bounds of 50 to the nearest 5 metres the answers would be:

• upper bound = 52.5
• lower bound = 47.5
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## Multiplying these Bounds

this is where it gets slightly more complicated but not by much.

to find the upper bound of a sum that is multiplying numbers, you need to:

upper bound x upperbound = largest possible answer

to find the lower bound of a sum when multiplying the numbers, you need to:

lower bound x lower bound = smallest possible number

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## Dividing these Bounds

to find the upper bound of a sum when dividing the numbers, you need to:

upper bound / lower bound = largest possible answer

to find the lower bound of a sum when dividing the numbers, you need to:

lower bound / upper bound = smallest possible answer

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