1. Science Mathematical Skills I Rounding Rules Pro. Ignacio Anguera
Colegio Real de Panamá
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2. ROUNDING NUMBERS RULES
ROUNDING NUMBERS RULES
CASE 1 – Number Greater Than 5
If the number to the right of the least significant digit is GREATER THAN 5, round the least significant digit UP.
Rounding means making a number simpler but keeping its value close to what it was.
Example: rounded to five significant figures is
123460
Round the following numbers to 2 decimal places:
4.829
67.377
9.896
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3. ROUNDING NUMBERS RULES
ROUNDING NUMBERS RULES
CASE 2 – Number Lower Than 5
If the number to the right of the least significant digit is LESS THAN 5, keep the least significant digit SAME.
Rounding means making a number simpler but keeping its value close to what it was.
Example: rounded to three significant
Round the following numbers to 2 decimal places:
4.822
67.370
9.894
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4. ROUNDING NUMBERS RULES
ROUNDING NUMBERS RULES
CASE 3 – 5 Alone
If the number to the right of the least significant digit is EXACTLY 5 with no nonzero digits afterward, round the least significant digit UP if it is an ODD number; if it is EVEN, leave it unchanged.
Rounding means making a number simpler but keeping its value close to what it was.
Example: rounded to three significant
12340
Why does this rule exist? Because if the least significant digit is exactly 5, we should, on average, round the number up half the time, and down half the time; otherwise we risk an accumulation of round-off error in repeated calculations.
Round the following numbers to 2 decimal places:
4.825
67.375
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5. ROUNDING NUMBERS RULES
ROUNDING NUMBERS RULES
CASE 4 – 5 And Something
If the first figure dropped is EXACTLY 5, and there are any figures following the five that are not zero, then round the least significant digit UP
Rounding means making a number simpler but keeping its value close to what it was.
124000
Example: rounded to three significant
Round the following numbers to 2 decimal places:
4.8258
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6. ROUNDING NUMBERS RULES
ROUNDING NUMBERS RULES
Rounding Rules
If the first figure dropped is
Rounding means making a number simpler but keeping its value close to what it was.
Exactly 5
More Than 5
Less Than 5
digit UP
digit SAME
with no nonzero digits afterward
with any nonzero digits afterward
digit UP
Even
Odd
digit SAME
digit UP
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7. # of decimal places desired First figure to be dropped
ROUNDING NUMBERS RULES
PRACTICE!
NUMBER
# of decimal places desired
Last figure to be kept
First figure to be dropped
Rule
Number becomes
6.422 1
6.4
6.42
6.4872 2
6.997
6.6500
7.485
8.995
6.6501
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