How to remember rounding
To remember how to round learn this following poem
Underline the digit
Look next door
Five or more raise the score
Four or less just ignore
NOTE:
Change all the numbers to the right of the underlined number to zero.
Example 1
Round the number 1338 to the nearest hundred.
1328 Round to the nearest hundred
1328 Underline the digit (the hundreds column)
1328 Look next door
2 It’s not five or more. It’s four or less so INGORE.
1300 Keep underlined number the same. Change all the numbers to the right to a zero.
Answer: 1328 to the nearest hundred is 1300.
Example 2
Round `pi` to four decimal places
3.141592653589……….
3.141592653589………. Round to four decimal places
3.141592653589………. Underline the digit (of 4th decimal place)
3.141592653589………. Look next door
9 It’s five or more, so you must round up.
3.1416 5 becomes 6 and all the numbers to the right become zero.
Answer: `pi` rounded to four decimal places is 3.1416
Example 3
Round 28381 to the nearest thousand.
28381…. Round to thousand
28381…. Underline the digit (the thousand column)
28381…. Look next door
3 It’s not five or more. It’s four or less so IGNORE.
28,000 Keep underlined number the same. Change all the numbers to the right to a zero.
Answer: 28381 rounded to the nearest thousand is 28,000
Example 4
Round 28381 to the nearest hundred.
28381…. Round to hundred
28381…. Underline the digit (the hundred column)
28381…. Look next door
8 It’s five or more. So you must round up
28,400 3 becomes 4 and all the numbers to the right become zero.
Answer: 28381 rounded to the nearest hundred is 28,400
Example 5
Round 28381 to the nearest ten.
28381…. Round to ten
28381…. Underline the digit (the tens column)
28381…. Look next door
1 It’s not five or more. It’s four or less so IGNORE.
28,380 Keep underlined number the same. Change all the numbers to the right to a zero.
Answer: 28381 rounded to the nearest ten is 28,380
Example 6
Round 3.7380599 to 2 decimal places
3.7380599…. Rounded to 2 decimal places.
3.7380599…. Underline the digit
3.7380599…. Look next door
8 It’s five or more. So you must round up
3.7400000 3 becomes 4 and all the numbers to the right become zero.
Answer: 3.7380599 to 2 decimal places is 3.74
Example 7
Work out `sqrt59` on a calculator to one decimal place.
`sqrt59` on a calculator is 7.681145……
7.681145…… Round to one decimal place
7.681145…… Underline the digit
7.681145…… Look next door
8 It’s five or more. So you must round up.
7.7000 6 becomes 7 and all the numbers to the right become zero.
Answer: `sqrt59` to 1 decimal place is 7.7
