Boxi Math

Stage 2 · New Numbers / #7

Why Do Fractions Need a Common Denominator?

S-1 · Numbers are amounts S-3 · Units can be redefined S-6 · Mistakes are fine — try it
Coming soon

The video is in production. Follow along on GitHub to hear when it is out.

The idea

To add two lengths you first measure both with the same small step; 1/6 measures both 1/2 and 1/3 exactly, so 1/2 + 1/3 = 3/6 + 2/6 = 5/6.

A common mix-up

1/2 + 1/3 = 2/5 (add the tops, add the bottoms).

Where it stops working

The position doesn't work: on the number line 2/5 is smaller than 1/2, so adding something would have moved us backwards.

School year
China 5