Rounding Numbers
Round the number 91
90
Use benchmark numbers to estimate 234 + 789
200 + 780 = 980 OR 200 + 800 = 10 000
What is a whole number?
A number without a part (decimal or fraction)
1 550
One thousand, five hundred fifty
If you multiply this number by any other number the answer will always be the same
0
Round the number 679
700 or 680 would both work
Use the easiest benchmark numbers to estimate 6987 + 2736
7000 + 3000 = 10 000
Explain what is meant by a benchmark number?
A number that is familiar and easy to work with. It should have lots of zero digits for large numbers
10 000
ten thousand
It's between 1-10
It's less than 5
It's the sum of the digits 1 and 2
3
Round the number 3681
4000, 3700 or 3680 would all work
Use the easiest benchmark numbers to estimate 638 + 929 + 587
600 + 900 + 600 = 2 100
What does it mean to estimate?
To roughly judge or calculate a number by rounding it
16 500
sixteen thousand five hundred
It has 4 digits
The thousand digit is less than 3
The number is less than 2000
The digits in the hundreds, tens and ones are zeros
1000
Round 7701 to the nearest thousand
8000
Use the easiest benchmark numbers to estimate how much dirt you need inside the AREA of a garden box.
99 x 68
100 x 70 = 7 000 cm2
Find the DIFFERENCE using benchmark numbers
7897 - 3772 =
8000 - 4000 = 4000
OR
7900 - 3800 = 4 100
54 681
fifty four thousand, six hundred eighty one
It has 4 digits
The digit in the thousands place value is greater than 8
The value of the digits in the hundreds and tens are zeros
The ones digit is the difference of 20-12
9008
Round the number 13 234 to the nearest 10 000
13 000
Use Benchmark numbers to figure out how much area of fencing you need to go around your yard 153m + 875m + 153m + 462m =
150 + 150 + 800 + 500 = 1600 meters
Find the DIFFERENCE and SUM using the easiest benchmark numbers
1687 - 1232 =
1700 - 1200 = 500
1700 + 1200 = 2900
245 122
two hundred forty five thousand, one hundred twenty two
It has 4 digits
The thousands and hundreds place value are the same number which can be found by finding the sum of 4+4
The tens digit is less than 3 and greater than 1
The ones digit is the greatest number found in the first row of a hundreds chart
8829