2DP

NID 995.3

GLUM 48.41

DRAT 2.976

LUSH 4.556

BRUM 8.739

OZ 8.787

PLONK 2.721

REEM 0.3066

SLYTHY 0.2469

WELLY-WANG 0.23200

Round each of the numbers on the signs to 2 decimal places then add all of your answers together.

Rounding to 2 Decimal Places

A Mathematics Lesson Starter Of The Day


Topics: Starter | Approximation | Arithmetic | Rounding

  • Transum,
  •  
  • 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

Nid 995.30

Glum 48.41

Drat 2.98

Lush 4.56

Brum 8.74

Oz 8.79

Plonk 2.72

Reem 0.31

Slythy 0.25

Welly-wang 0.23

1072.29

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

Note to teacher: Doing this activity once with a class helps students develop strategies. It is only when they do this activity a second time that they will have the opportunity to practise those strategies. That is when the learning is consolidated. Click the button above to regenerate another version of this starter from random numbers.



Extension

Do you know how to round negative numbers? 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.



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Laptops In Lessons

Teacher, do your students have access to computers such as tablets, iPads or Laptops?  This page was really designed for projection on a whiteboard but if you really want the students to have access to it here is a concise URL for a version of this page without the comments:

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However it would be better to assign one of the student interactive activities below.

Laptops In Lessons

Here is the URL which will take them to a related student activity.

Transum.org/go/?to=roundingsnap

Student Activity

 

Curriculum Reference

See the National Curriculum page for links to related online activities and resources.


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