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"Sum" Trick

In the book Ten Black Dots book, there are a total of 55 black dots. Normally, to find that answer, you would add the numbers together.

But did you know there is an easier way? Take 10 and divide it by 2. That equals 5. Multiply 10 x 5 and you get 50 then add in the 5 which equals 55. Too confusing? Well let's look at it in groups that equal 10.


As illustrated above, 10 is by itself so it is 10. Then if we group the numbers so that each group equals ten, we have four additional sets. All together, we have five groups of ten with five left over which equals 55.   5 x 10 = 50 + 5 = 55

This will work for every sequence of consecutive numbers which begins with one and contains an even set. In other words, sets that contain 2, 4, 6, 8, 10, 12... numbers. Merely divide the largest number by 2; multiply the largest number by the quotient, and then add the quotient.


Example:  14, 13, 12, 11, 10,  9,  8,  7,  6,  5,  4,  3,  2, 1

This will also work for an odd numbered sequence like 11 but the formula or quick trick for finding the sum is a little different. As seen below, we again divide 11 by 2, which 5.5 or rounded up equals 6. Again we group sets of two that equal 11. There are five groups plus 11 by itself so that makes a total of six groups.
Since there are no numbers left by themselves, simply multiply 11 by 6 (the rounded up quotient) to get the sum which is 66.

I love to write a series of consecutive numbers which begin with one on the board, and have the students find the answer using their calculators while I do the math in my head. Of course, they are amazed and swear that I have memorized the answer. I then ask me to give me a series (not off the wall or so large that it would take forever to use the calculator) and again I quickly give them the answer. I then teach them that math trick.

Students love "tricks" like this, but I always burst their bubble by telling them mathematicians are astute people. That's why they are always looking for faster, quicker, and smarter ways to do math!

A Go Figure Debut for A Poet Who Is New!

Theresa's TPT Store
Today’s post features a Board Certified Teacher from North Carolina. (As most of you know, Board Certification requires a great deal of work!) Theresa has taught Reading Recovery, been a third grade resource teacher, has taught first and second grade, as well as a first and second multi-age class. She has been teaching for 19 years and says she still loves what she does!!! Besides teaching, she enjoys spending time with her family and taking care of her two cats that are named Cindy Lou Who and Boots.

Her Teachers Pay Teachers store, Theresa’s Teaching Tidbits, is unique in that it contains several resources that showcase poems. Theresa even features a poem of the week and offers a bundle of these poem activities in the resource entitled: Poem of the Week Bundle. It includes all four of her Poem of the Week elementary products at a discounted price. They are:
Discounted Bundle
  • A Kind and Caring Classroom: Poems of the Week that Promote Good Character
  • Science Poems and Activities for Primary Grades
  • Patriotic Poems and Activities for Primary Grades
  • Fall Poems and Activities for Primary Grades
She suggests using these poems as a part of your weekly routine to teach comprehension, phonemic awareness, phonics, vocabulary and fluency.

Free Resource
Since her students love word searches, Theresa has created a ten page freebie called Word Searches: Fry Word Finds. She uses word searches to help early readers increase instant recognition of high-frequency words. Each word search in this free resource features ten of the 100 most used words in reading and writing and includes three different word searches with answer keys. These would be perfect for a center or for those who finish early!

Additionally, Theresa has a blog that bears the same name as her store. I loved reading her August 27th post about having a school garden. Since I teach at a college, we have gardens everywhere, but they aren’t created or maintained by the students which might be a good thing. If you take time to look at her blog, you will see pictures of her current classroom which might give you some ideas for arranging yours. In addition, she shares some books that made it to her front porch over the summer. I get the idea she loves reading books to her students!

In her August 20th post, Theresa gives you a step-by-step picture tutorial on how to make four-pocket folders that she uses in her writing workshop. (You’ll have a good laugh on why she didn’t make a video tutorial.) She even has free labels for these folders that you can download. You’ll just have to check out her blog to find out where and how…something I highly recommend that you do!