No Guesstimating?
Some people think rounding and estimating are interchangeable. Although they are not the same thing, they do have the same goal: making a manageable or presentable number.
Rounding
When you round a number, you are looking for the nearest ten (or tenth), hundred (or hundredth), thousand (or thousandth), etc. depending on what the question is asking. Rounding is really easy (as long as you know your place value!) because you are either going up or down. Your deciding number is 5. If the number is below 5, round down. If the number is 5 or above, then round up. Here are some examples:
Notice where you round depends on the place value asked.
The numbers in red show you what numbers are being considered when rounding. As you can see, rounding is determined by the numbers to the right of the place value being asked.
Estimating
To estimate, you are making an educated guess based on the information you have. For example, if you know the dog biscuit jar holds twenty biscuits and it looks almost full, definitely more than half-full, a good estimate would be 15.
Remember: Estimating’s purpose is not to give an exact, calculated answer, but a reasonable answer based on the information given.
Estimate how many attended the convention.
Liesel attended a Lifetime Learning Convention this summer. She knows the convention center holds up to 1,000 people, but it wasn’t a completely sold out event. Liesel estimates approximately 900 people attended based on crowd size and ticket sales.