There are infinitely many pairs.
Two examples are 55000 and 55000, or 100000 and 10000.
The idea is to round each of the numbers - in this case to the nearest multiple of 10 - then do the addition in your head.
The numbers are 17 and 18.
The numbers are 26 and 28.
Notice that each of the three numbers is rather close to 9,000. The estimated sum is 27,000.
210
The numbers are 4, 5 and 6.
The sum is where two or more numbers are added together to give a total.
Quantifying the sum of two numbers is usually simple to do. You take the given sum of the two numbers and subtract it with one given unsummed number. This will give you the other number.
3874 + 1845 = 5719 is the actual sum. I'm not sure where the 'estimated sum' comes into it.
They are 36 and 64
They are 36 and 64
55