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Edu-Primes
  • 1 year ago
Transcript
00:00Hi kids today, we will be making nearest estimates for addition and subtractions
00:13Using rounding off to the nearest 10
00:18Remember
00:19Neither use your fingers nor your calculator
00:24We will be calculating orally
00:27So let's start
00:30You
00:32Have to add 13 and 10
00:3713 is midway between two tens
00:42So we will round off 13 to nearest 10
00:5013 will be rounded down to 10 as it's below the 5 mark
00:58Now add the rounded off figures to calculate the estimate
01:0610 plus 10 equals to 20
01:11So the nearest estimate of
01:1513 plus 10 is 20
01:19Now compare the estimate with the actual sum
01:25Actual sum is
01:2813 plus 10 equals
01:3223
01:33Yeah
01:35Our estimate is very near
01:38Good
01:40Now let's take another example
01:45You have to
01:47Add 34 and 56
01:5156
01:53Here both the numbers are midway between two tens
01:59So we will round off them
02:04Rounding off 34 to the nearest 10
02:08We will get 30 as 34 is below the 5 mark
02:17Rounding off 56 to the nearest 10
02:20We will get 60 as
02:2456 is above the 5 mark
02:28Now add the rounded off figures to calculate the estimate
02:3630 plus 60 gives us 90
02:42so the nearest estimate of
02:4534 plus 56 is
02:4990
02:51Now 34 plus 56 gives us 90. Oh
02:58Wow
03:00Here the estimate and actual sum are the same
03:06Good
03:08Now let's take another example
03:14We have to subtract
03:1773 from 82
03:21Here both the numbers are midway between the two tens
03:28So first we will be rounding off them
03:35Rounding off 73 to nearest 10. We will get 70 as
03:4273 is below 5 mark
03:47Rounding off 82 to nearest 10
03:52We will get 80 as 82 is below the 5 mark
04:00Now subtract the rounded off figures to calculate the estimate
04:0880 minus 70 we will get 10
04:14So the nearest estimate of 82 minus 73 is 10
04:22Now let's compare the estimate with the actual answer
04:2982 minus 73 is 9
04:34So your estimate is very very near
04:38Our estimate was 10 and the actual difference is 9
04:45Good
04:48Now let's take another example
04:52We have to add
04:5585 and
04:5761
04:59Here both the numbers are midway between two tens
05:04So we will be rounding off them
05:08Rounding off 85 to the nearest 10. We get 90 as
05:1685 is on the 5 mark
05:21Rounding off 61 to the nearest 10 will give us 60 as
05:2861 is below the 5 mark
05:33Now add the rounded off figures
05:3890 plus 60
05:41equals
05:42150
05:44Now let's compare the estimate with the actual answer
05:5085 plus 61
05:52equals
05:54146
05:56So your estimate is very near
06:00So what have we learned
06:02We have learned to
06:04Make rough estimates by rounding off the numbers it
06:10Helps us in fast
06:12calculations when
06:14necessary
06:15Now you may go ahead and take a quiz to learn more
06:19Bye. Bye