Mike Jacobs
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mikejacobs.bsky.social
Mike Jacobs
@mikejacobs.bsky.social
460 followers 43 following 550 posts
Math teacher in Ontario/Mountaineer/Munroist/Exiled Yorkshireman/Dad to two great kids.
Creator of Yohaku Puzzle https://www.yohaku.ca/
Author of Onwards and Upwards. https://tinyurl.com/OnwardsUpwardsHills .
#RunEveryDay
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mikejacobs.bsky.social
Try this shady #yohaku. Fill in cells with 9 different integers to get products shown in each row/column AND sum of 4 shaded cells is -5. #mathsky #iTeachMath
Use 9 different integers in a 3 by 3 grid. The numbers in the top row multiply to -171. The numbers in the middle row multiply to 136. The numbers in the bottom row multiply to 30. The numbers in the left column multiply to -76. The numbers in the middle column multiply to 255. The numbers in the right column multiply to 36. The sum of the integers in the 2 by 2 square at the top left of the grid is -5.
November 27, 2025 at 11:50 AM
mikejacobs.bsky.social
I gave this #OpenMiddle task to my students: use the digits 0 to 9 at most once only to make each statement true. It really got them thinking carefully about the exponent laws we learnt about.
A series of incomplete statement using exponent laws. Student work on a whiteboard showing exponent laws. Student work on a whiteboard showing exponent laws.
November 27, 2025 at 3:27 AM
mikejacobs.bsky.social
Start your day with this #yohaku. Fill in cells with 9 different factors of 342 to get totals shown in each row/column. #mathsky #iTeachMath
Use 9 different factors of 342 in a 3 by 3 grid. The numbers in the top row add to 34. The numbers in the middle row add to 41. The numbers in the bottom row add to 78. The numbers in the left column add to 77. The numbers in the middle column add to 26. The numbers in the right column add to 50.
November 26, 2025 at 12:09 PM
mikejacobs.bsky.social
"Start your day with this #yohaku. Fill in cells with 9 different whole numbers to get products shown in each row/column. More free puzzles and books/ebooks for all ages can be found at yohaku.ca
Use 9 different whole numbers in a 3 by 3 grid. The numbers in the top row multiply to 90. The numbers in the middle row multiply to 320. The numbers in the bottom row multiply to 63. The numbers in the left column multiply to 420. The numbers in the middle column multiply to 32. The numbers in the right column multiply to 135.
November 25, 2025 at 12:07 PM
mikejacobs.bsky.social
Saw these unusual floor tiles at the weekend. What is the ratio of the area of the beige hexagon to the area of the brown octagon?
A mixture of different floor tiles of different shapes and sizes.
November 24, 2025 at 5:00 PM
mikejacobs.bsky.social
Start your week with this #yohaku. Fill in cells with 9 different factors of 224 to get totals shown in each row/column. #mathsky #iTeachMath
Use 9 different factors of 224 in a 3 by 3 grid. The numbers in the top row add to 37. The numbers in the middle row add to 74. The numbers in the bottom row add to 53. The numbers in the left column add to 64. The numbers in the middle column add to 24. The numbers in the right column add to 76.
November 24, 2025 at 12:13 PM
mikejacobs.bsky.social
Here's a #yohaku to take you into the weekend. Fill in cells with 16 different factors of 980 to get totals shown in each row/column AND shaded cells contain square numbers. #mathsky #iTeachMath
Use 16 different factors of 980 in a 4 by 4 grid. The numbers in the top row add to 28. The numbers in the second row add to 315. The numbers in the third row add to 221. The numbers in the bottom row add to 360. The numbers in the left column add to 60. The numbers in the second column add to 264. The numbers in the third column add to 287. The numbers in the right column add to 313. The central four cells contain square numbers.
November 21, 2025 at 11:46 AM
mikejacobs.bsky.social
I gave this warm up problem to my classes today.
It was a big hit!
A right triangle with a hypotenuse of 2245 cm and a shorter side of 2244 cm. The smallest side is labeled 'x' and has to be calculated.
November 21, 2025 at 12:55 AM
mikejacobs.bsky.social
Try this shady #yohaku. Fill in cells with 9 different integers to get products shown in each row/column AND sum of 4 shaded cells is -9. #mathsky #iTeachMath
Use 9 different integers in a 3 by 3 grid. The numbers in the top row multiply to 222. The numbers in the middle row multiply to 276. The numbers in the bottom row multiply to 40. The numbers in the left column multiply to -111. The numbers in the middle column multiply to 230. The numbers in the right column multiply to -96. The sum of the integers in the 2 by 2 square at the top left of the grid is -9.
November 20, 2025 at 11:47 AM
mikejacobs.bsky.social
Start your day with this #yohaku. Fill in cells with 9 different factors of 364 to get totals shown in each row/column.
#mathsky #iTeachMath
Use 9 different factors of 364 in a 3 by 3 grid. The numbers in the top row add to 49. The numbers in the middle row add to 43. The numbers in the bottom row add to 55. The numbers in the left column add to 28. The numbers in the middle column add to 63. The numbers in the right column add to 56.
November 19, 2025 at 11:52 AM
mikejacobs.bsky.social
I'm very happy to be supporting Maths Week England @maths_week Check out their website for an amazing set of resources for this week, including some yohaku puzzles for all ages! #MWE
November 18, 2025 at 1:04 PM
mikejacobs.bsky.social
Start your day with this #yohaku. Fill in cells with 9 different whole numbers to get products shown in each row/column. More free puzzles and books/ebooks for all ages can be found at yohaku.ca
Use 9 different whole numbers in a 3 by 3 grid. The numbers in the top row multiply to 936. The numbers in the middle row multiply to 28. The numbers in the bottom row multiply to 102. The numbers in the left column multiply to 273. The numbers in the middle column multiply to 96. The numbers in the right column multiply to 102.
November 18, 2025 at 12:05 PM
mikejacobs.bsky.social
Start your week with this #yohaku. Fill in cells with 9 different factors of 450 to get totals shown in each row/column. #mathsky #iTeachMath
Use 9 different factors of 450 in a 3 by 3 grid. The numbers in the top row add to 26. The numbers in the middle row add to 15. The numbers in the bottom row add to 40. The numbers in the left column add to 39. The numbers in the middle column add to 8. The numbers in the right column add to 34.
November 17, 2025 at 11:49 AM
mikejacobs.bsky.social
Here's a #yohaku to take you into the weekend. Fill in cells with 16 different factors of 540 to get totals shown in each row/column AND shaded cells contain triangle numbers. #mathsky #iTeachMath
Use 16 different factors of 540 in a 4 by 4 grid. The numbers in the top row add to 40. The numbers in the second row add to 103. The numbers in the third row add to 90. The numbers in the bottom row add to 113. The numbers in the left column add to 189. The numbers in the second column add to 61. The numbers in the third column add to 84. The numbers in the right column add to 12. The central four cells contain triangle numbers.
November 14, 2025 at 1:21 PM
mikejacobs.bsky.social
Try this shady #yohaku. Fill in cells with 9 different integers to get products shown in each row/column AND sum of 4 shaded cells is -4. #mathsky #iTeachMath
Use 9 different integers in a 3 by 3 grid. The numbers in the top row multiply to -104. The numbers in the middle row multiply to 154. The numbers in the bottom row multiply to 63. The numbers in the left column multiply to 182. The numbers in the middle column multiply to -132. The numbers in the right column multiply to 42. The sum of the integers in the 2 by 2 square at the top left of the grid is -4.
November 13, 2025 at 11:45 AM
mikejacobs.bsky.social
Start your day with this #yohaku. Fill in cells with 9 different factors of 350 to get totals shown in each row/column. #mathsky #iTeachMath
Use 9 different factors of 350 in a 3 by 3 grid. The numbers in the top row add to 42. The numbers in the middle row add to 87. The numbers in the bottom row add to 76. The numbers in the left column add to 76. The numbers in the middle column add to 79. The numbers in the right column add to 50.
November 12, 2025 at 11:49 AM
mikejacobs.bsky.social
Start your day with this #yohaku. Fill in cells with 9 different whole numbers to get products shown in each row/column. More free puzzles and books/ebooks for all ages can be found at yohaku.ca
Use 9 different whole numbers in a 3 by 3 grid. The numbers in the top row multiply to 56. The numbers in the middle row multiply to 312. The numbers in the bottom row multiply to 84. The numbers in the left column multiply to 84. The numbers in the middle column multiply to 48. The numbers in the right column multiply to 364.
November 11, 2025 at 11:59 AM
mikejacobs.bsky.social
I came across a really nice way of visually showing the sum of the first n square numbers. Details in this blog:
themathguy.blogspot.com/2025/11/the-...
The Sum of the First n Square Numbers
One of the things I like to do as a teacher is provide visual proofs of why certain formulas work. A nice one that I use a lot in high scho...
themathguy.blogspot.com
November 10, 2025 at 3:57 PM
mikejacobs.bsky.social
Start your week with this #yohaku. Fill in cells with 9 different factors of 120 to get totals shown in each row/column. #mathsky #iTeachMath
Use 9 different factors of 120 in a 3 by 3 grid. The numbers in the top row add to 57. The numbers in the middle row add to 85. The numbers in the bottom row add to 46. The numbers in the left column add to 10. The numbers in the middle column add to 90. The numbers in the right column add to 88.
November 10, 2025 at 11:45 AM
mikejacobs.bsky.social
Here's a #yohaku to take you into the weekend. Fill in cells with 16 different factors of 432 to get totals shown in each row/column AND shaded cells contain square numbers. #mathsky #iTeachMath
Use 16 different factors of 432 in a 4 by 4 grid. The numbers in the top row add to 14. The numbers in the second row add to 43. The numbers in the third row add to 148. The numbers in the bottom row add to 231. The numbers in the left column add to 43. The numbers in the second column add to 70. The numbers in the third column add to 177. The numbers in the right column add to 146. The central four cells contain triangle numbers.
November 7, 2025 at 11:48 AM
mikejacobs.bsky.social
Try this shady #yohaku. Fill in cells with 9 different integers to get products shown in each row/column AND sum of 4 shaded cells is -5. #mathsky #iTeachMath
Use 9 different integers in a 3 by 3 grid. The numbers in the top row multiply to -210. The numbers in the middle row multiply to -18. The numbers in the bottom row multiply to 44. The numbers in the left column multiply to -42. The numbers in the middle column multiply to 495. The numbers in the right column multiply to -8. The sum of the integers in the 2 by 2 square at the top left of the grid is -5.
November 6, 2025 at 11:51 AM
mikejacobs.bsky.social
Start your day with this #yohaku. Fill in cells with 9 different factors of 910 to get totals shown in each row/column. #mathsky #iTeachMath
Use 9 different factors of 910 in a 3 by 3 grid. The numbers in the top row add to 78. The numbers in the middle row add to 84. The numbers in the bottom row add to 218. The numbers in the left column add to 197. The numbers in the middle column add to 22. The numbers in the right column add to 161.
November 5, 2025 at 11:53 AM
mikejacobs.bsky.social
"Start your day with this #yohaku. Fill in cells with 9 different whole numbers to get products shown in each row/column. More free puzzles and books/ebooks for all ages can be found at yohaku.ca
Use 9 different whole numbers in a 3 by 3 grid. The numbers in the top row multiply to 36. The numbers in the middle row multiply to 52. The numbers in the bottom row multiply to 765. The numbers in the left column multiply to 390. The numbers in the middle column multiply to 136. The numbers in the right column multiply to 27.
November 4, 2025 at 11:43 AM
mikejacobs.bsky.social
Start your week with this #yohaku. Fill in cells with 9 different factors of 294 to get totals shown in each row/column. #mathsky #iTeachMath
Use 9 different factors of 294 in a 3 by 3 grid. The numbers in the top row add to 107. The numbers in the middle row add to 98. The numbers in the bottom row add to 36. The numbers in the left column add to 76. The numbers in the middle column add to 106. The numbers in the right column add to 59.
November 3, 2025 at 11:44 AM
mikejacobs.bsky.social
Don't forget to turn ALL your clocks back today!
November 2, 2025 at 7:43 PM