Final answer:
The least whole number that rounds to 850 is 845, considering that any number from 845 to 854 rounds to 850 when applying the standard rules of rounding to the nearest ten.
Step-by-step explanation:
The student's question appears to involve the concept of rounding numbers to the nearest ten. However, it seems there might be confusion in the question presented. The question asks for the least whole number that rounds to 850 when rounded to the nearest ten, but the example given (640 rounding to the nearest ten) does not relate to the primary question. Generally, to round a number to the nearest ten, you would look at the one's place. If the one place is 5 or higher, you round up. If it's 4 or lower, you round down.
For the question at hand, any number from 845 to 854 will round to 850 when rounded to the nearest ten. Therefore, the least whole number that would round up to 850 would be 845, as it is the smallest number in that range.
It's important to understand the rounding-off process within the context of place value and significant figures. When performing calculations, if the numbers have different numbers of decimal places, typically you would round based on the number with the least number of decimal places. This ensures that the result maintains a relevant level of precision without overestimating the accuracy of the calculated values.