Yesterday, I was going to use the height of a penny in a math question on a quiz so I googled "width of a penny". It said it was 3/4 inch. That wasn't what I wanted, but I liked the number. I went to bed thinking about it and woke up with this....
Maybe an actual original idea for the #MTBoS?
There has been recent discussion on blogs and twitter about how to teach dividing by fractions besides just telling the kids to multiply by the reciprocal - the why part.
It got me to thinking: how many pennies would line up on a ruler? A penny's diameter is 3/4 inch, so I did 12 divided by 3/4 but really multiplied by the reciprocal 12 times 4/3 and I got 16. Sixteen pennies should fit on a ruler.
So, then I thought about it some more:
Next I multiplied by 3 and got 15 - what the heck?! Now, mind you, I woke up thinking all this at 6 am on a Saturday morning. I knew I was wrong but it seemed to work.
It lead me to a joke (again early morning):
What does 1 penny plus 1 quarter equal? An inch :) I like it - that's original too!
So, then I was thinking about 2 pennies. Two pennies would be an inch and half so four pennies would be three inches, but then I have a whole inch left over and a penny is only 3/4 inch so I would have room for 1 penny with 1/4 left over -ahhhhhh - there it is. I would have three 1/4's leftover and that equals my sixteenth penny.
I went wrong in thinking that four fourths makes the whole. Only three fourths makes a whole penny.