9514 1404 393
Answer:
about $12
Explanation:
For estimating purposes, you often want to round numbers to 1 or 2 significant digits. The price $4.23 can be rounded to $4. Then 3 such items will cost about ...
3×$4 = $12
You spent about $12.
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Additional comments
Along with an estimate, you often want to estimate the error in the estimate. Here, a first approximation of the error is that it is 3 × $0.20 too low. That is, the estimate of spending will be closer if we revise it upward by $0.60 to $12.60.
We know that even that estimate is low by $0.03 on each of the 3 items, so a better approximation of the spending is $12.60 +0.09 = $12.69.
This has accounted for all of the errors, so the actual spending was $12.69.