Decimal records

Decimal records

Pencil and paper
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This task is about rounding decimal numbers to a given number of decimal places.


Source: office.microsoft.com/clipart

Swimming world records are now recorded in seconds to the nearest 2 decimal places. Before 1970 they were only recorded to 1 decimal place. Modern electronic equipment can record results to 3 decimal places.

Write each of these times to the number of decimal places indicated.

a) 26.872 seconds to 2 decimal places is __________ seconds

b)		  
58.449 seconds to 1 decimal place is __________ seconds

c)		  
24.1 to seconds to 3 decimal places is __________ seconds

d)		  
29.145 seconds to 2 decimal places is __________ seconds

e)		  
54.357 seconds to 1 decimal place is __________ seconds

f)		  
56.954 seconds to 1 decimal place is __________ seconds

 

Task administration: 
This task is completed with pencil and paper, and other equipment.
Levels:
4, 5
Curriculum info: 
Maths, Number and Algebra, Number Knowledge
Keywords: 
decimal places, rounding, place value
Description of task: 
Students round six different decimal numbers of swimming times to a given number of decimal places.
Answers/responses: 

 

Y10 (03/2004)
a) 26.87 easy
b) 58.4 moderate
c) 24.100 moderate
d) 29.15 moderate
e) 54.4 moderate
f) 57.0 difficult
Diagnostic and formative information: 
  Common error Likely misconception
a) 0.26872 or 2687.2 Moves the decimal point 2 places (similar errors for b) - f)).
b) 58.5 Rounds to 2 decimal places (58.45), then to one decimal place (58.5).
b)
e)
f)		 58.45
54.36
56.95		 Gives the answer to an incorrect number of decimal places.
c)
f)		 24.1
57 (or 57.)		 Misses zeros that need to be present as place value holders to get the correct number of decimal places.
d)
e)
f)		 29.14
54.3
56.9		 Rounds 5 down rather than up.