How do I find an estimate for the sum of the numbers 622,78,81,111, to the nearest 10.?

2 Answers
Nov 4, 2017

620 + 80 + 80 + 110 = 890

Explanation:

When we're rounding any number to the nearest ten, we'll want to first find the two tens that it's in between.

For our problem:

  • 622 is between 620 and 630
  • 78 is between 70 and 80
  • 81 is between 80 and 90
  • 111 is between 110 and 120

Next, we want to find which of those tens each number is closest to. We'll round the number to that particular ten.

  • 622 is closer to 620 than 630, so we round it to 620
  • 78 is closer to 80 than 70, so we round it to 80
  • 81 is closer to 80 than 90, so we round it to 80
  • 111 is closer to 110 than 120, so we round it to 110

Finally, we can use our rounded addends to find an estimated sum:

620+80+80+110=890

Nov 4, 2017

620," "80," "80," "110

Explanation:

If a number is to be rounded to the nearest 10, the answer must be a multiple of 10. The last digit must be a 0

To decide whether to round up or down, look at the digit in the units place. If it is 5 or more, round up. If it is 4 or less, round down.

622 " " rarr 620

78 " "rarr 80

81 " "rarr 80

111" "rarr 110