Question

"to replace a number with another number that tells about how many or how much". What is ths operation called?

Answer 1

The operation is known as rounding of a number.

This means basically if i measure the temperature of a city and it comes out to be 22.9 degrees. I will round it of to 30 degrees or the amount of significant figures i am designated with.

Similarly if its 22.85 and i have to round of to 3 significant figures it becomes 22.9 degrees.

ROunding off is obviously done watching to which digit we have to.

Answer 2

This operation is called rounding. 

For example, if I scored 97.9 points on a math test, I could round it up to 98. Or, if I scored 92.1 points, then I could round it down to 92. In both cases, the real math scores (both of which are decimals) are replaced by different, whole numbers.