<u><em>Answer:</em></u>
The estimated sum is 90
<u><em>Explanation:</em></u>
To get the estimated sum, we will round the given numbers to the nearest tens
<u>Remember that:</u>
To round to the nearest tens, we check the digit in the units place
If this digit is less than 5, we round down
If the digit is greater than or equal to 5. we round up
<u>Now, for the given numbers:</u>
<u>52:</u> The number in the units place is 2 which is less than 5, so we round the 52 down to 50
<u>39:</u> The number in the units place is 9 which is greater than 5, so we round the 39 up to 40
<u>Now, it is easier to compute the estimated sum using the rounded numbers:</u>
50 + 40 = 90
Hope this helps :)