Depth 1 · 32 s
Groups and arrays
Four bags of six is six added four times - 24. Lined up in rows the bags make an array, and turning the array shows 4 × 6 is the same as 6 × 4.
About this video
Multiplying is a quick way of adding the same number again and again. Four bags with six in each bag is 6 + 6 + 6 + 6, which is 24, and we write it 4 × 6 = 24: four groups of six. This short animation shows the bags first, then lines each bag up as one row. Four rows of six dots make a rectangle called an array.
Arrays show something adding up the groups one by one doesn't: turn the array a quarter of a turn and it becomes six rows of four. Nothing was added or taken away, so 4 × 6 = 6 × 4. The order of multiplying doesn't matter. The video ends with multiplying by ten. Every digit moves one place to the left and a zero fills the ones place, so 24 × 10 = 240. That is place value at work: each place is worth ten times the one to its right. This video goes with the Rows and Groups lesson of Numbers Level 1 on Knaph.
This video shows depth 1 of Multiplication.
Learn MultiplicationTranscript
- 0:00Four bags, six in each. How many in all?
- 0:04Add six, four times. Six, twelve, eighteen, twenty-four.
- 0:09Line the bags up in rows. Four rows of six make an array.
- 0:15Turn the array. Now it's six rows of four. Still twenty-four.
- 0:21And times ten? Every digit moves one place to the left.
- 0:27Multiplying is adding the same number again.