Rounding 2DP

A Maths Starter of The Day

Round each of the following to 2 decimal places

601.7
60.25
1.300
3.957
7.411

2.149
4.512
0.2067
0.2341
0.20780

Now add all of your answers together.

 

 


Topics: Starter | Approximation | Arithmetic | Rounding

  • Transum,
  • Friday, June 20, 2014
  • "A teaching point worth making is that in long, multi-step calculations it is only usually the final answer that should be rounded. If each of the answers to the intermediate steps are rounded the rounding errors produced will have a cumulative detrimental effect on the accuracy of the final answer."

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Answers

601.70
60.25
1.30
3.96
7.41

2.15
4.51
0.21
0.23
0.21

681.93

Would you have got the same answer if you had added all of the original numbers together then rounded off the answer?

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Laptops In Lessons

Here is the URL for a concise version of this page without comments or answers.

Transum.org/go/?Start=June20

Here is the URL which will take them to a student version of this activity.

Transum.org/go/?to=roundingdp

 

 

Extension

Do you know how to round negative numbers? When rounding to one decimal place, if values exactly half way between get rounded up should -37.25 be rounded to -37.2 or -37.3? Does ‘rounded up’ mean rounded to the larger value or the value furthest away from zero?

A system of rounding commonly used in bookkeeping and some computing procedures is called ‘round half to even’. In this system half way values are rounded either up or down in order to make the last digit an even number.

So, for example, 37.25 becomes 37.2, 37.15 also becomes 37.2 and −37.25 becomes −37.2 without any doubt.

This method of rounding is also useful when rounding values in large data sets as it evens out the rounding ups and rounding downs for the half way values.