Add 'Em

Add up all of the numbers from
1 to 42

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A Mathematics Lesson Starter Of The Day


Topics: Starter | Algebra | Number | Problem Solving | Sequences

  • Kerei James, NZ
  • It is an excellent resource.
  • S.W, Redbourn Junior
  • I would have this starter up when the children enter the room. They work out the answer on white boards and as soon as they have finished they write their initials against the highest number available in a list of numbers from 1 to 10 on another board - the TOP TEN list. When the TOP TEN is full up we stop and look at the answer together.
  • Nicola, Neilston Primary School
  • My class counted them all up and got the answer 703 then double checked it with a calculater and they were correct.
  • Class A, Furness Vale Primary School
  • We get 1176 doubled checked on a calculator.
  • Cody Reimer, Acadia Junior High, Canada
  • The correct answer is 820 like it says at the bottom. The formula you use is for consecutive sum.
    sum = 40(40+1)/2
    sum = 1640/2
    sum = 820.
  • Ray Dunne, Ireland
  • Answering the question as written ,assuming there is no word play and using universal basic addition I concur with 1176. I would prefer your method though as my sallery would be greatly increased.
  • Ray Dunne, Ireland
  • While Cody from Canada has the formula correct he has inputted the wrong information . if you change 40 and 41 for 48 and 49 then you get 1176 which is the correct answer.
  • Jonathan, Wales
  • The triangular number formula is correct.
    However I would like to point out that the numbers used sometimes differ hence why different people are saying different results.
  • Mrs Zaker - Teacher Of Maths, Tolworth Girls' School, London UK
  • Using Carl Friedrich Gauss's method: we have 22 pairs that add to 46 (half of 45 is 22) PLUS the 23rd number (which is 23)
    45 + 1 = 46
    44 + 2 = 46
    43 + 3 = 46
    so 22 x 46 = 1012
    add on 23 that gives 1035.
  • Transum,
  • Please note that each time this page is loaded the number of numbers in the question changes. Consequently the solutions suggested here in the comments will refer to different variations of this starter. Thanks Jonathan for pointing this out. Thanks also for the comments and explanations of the methods you used. keep them coming!
  • Angus Dresner, O.K.C.M.S
  • Just today I found this method myself. If you half the biggest number which in my case is 56 you get 28. then add .5 to get 28.5. Multiply the two numbers together to get 1596.
  • Uzma, Barking
  • Hi all
    I found it 1176 . I want to tell you the way I followed. I think it is the easiest method. First add all th 10s in the sum. Then find how many 1s,2s.......8s in the sequence. These numbers coming 5 times in the sequence, so multiply each number from 1-8 with 5.and add all in the sum of 10s. Finally add 9x4, as 9 appear only 4 time in the sequence.

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Laptops In Lessons

Teacher, do your students have access to computers?
Do they have iPads or Laptops in Lessons?

Whether your students each have a TabletPC, a Surface or a Mac, this activity lends itself to eLearning (Engaged Learning).

Laptops In Lessons

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Student Activity

The famous Mathematician Carl Gauss found a quick way to perform this type of calculation when he was a boy; a long time before calculators!
Students could search the web for details of this story.

Carl Gauss



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