Run sheet

Prime Factorization and Exponential Notation — Prime Factorization

Grade 7 · Lesson 3 · 23 slides · blocked practice

The big idea

Every whole number above 1 breaks down into primes in exactly one way. A prime has no factors but 1 and itself.

Slide by slide

#On the screenWhat you say
1Today — WARM-UPPoint at the five parts. Name where we are.
2Write the first four multiples of 11.Boards up on three. This is yesterday's work — Multiples. Do not help each other; I need to see what each of you kept.
311, 22, 33, 44 answer — own slideShow me. Everyone at once. Check your own board against this.
4Today — I DOWe are at I DO. Boards down and flat.
5Every whole number above 1 breaks down into primes in exactly one way. A prime has no factors but 1 and itself.Read this out. Do not explain it yet — the example explains it.
660 = 6 × 10 build 1 of 5Break down 60. I take any factor pair.
760 = 6 × 10
60 = 2 × 3 × 10 build 2 of 5
Neither is prime, so I keep going. 6 = 2 × 3.
860 = 6 × 10
60 = 2 × 3 × 10
60 = 2 × 3 × 2 × 5 build 3 of 5
10 = 2 × 5.
960 = 6 × 10
60 = 2 × 3 × 10
60 = 2 × 3 × 2 × 5
60 = 2 × 2 × 3 × 5 build 4 of 5
All four are prime. I order them.
1060 = 6 × 10
60 = 2 × 3 × 10
60 = 2 × 3 × 2 × 5
60 = 2 × 2 × 3 × 5
unique: 2 × 2 × 3 × 5 build 5 of 5
Starting from 4 × 15 instead gives the same primes. Always does.
11Write 36 as a product of primes.Now the same thing on a new one. Watch — nothing on your boards.
1236 = 4 × 9.
4 = 2 × 2 and 9 = 3 × 3.
36 = 2 × 2 × 3 × 3 answer — own slide
I say every step aloud as I write it. The board keeps all of it.
13Today — WE DOWe are at WE DO. Boards up.
14Write 84 as a product of primes.Any starting pair is allowed. Keep splitting until every factor is prime. Boards up.
1584 = 4 × 21
4 = 2 × 2, 21 = 3 × 7
2 × 2 × 3 × 7 answer — own slide
Boards up. Everyone at once — check yours against this.
16Write 45 as a product of primes.One of these primes appears twice.
1745 = 9 × 5
9 = 3 × 3
3 × 3 × 5 answer — own slide
Boards up. Everyone at once — check yours against this.
18Today — YOU DOWe are at YOU DO. Boards down, books open.
19Dimensions 7A — page 4Open your books to this page. Wait — do not start yet.
20Do — page 4These are the book's own problems, same type as the three we have just done. Work them in the book.
21Today — CLOSURELast part. Answers up.
22“Is every factor on my list prime?”This is the question to ask yourself every time, not just today.
23Write 50 as a product of primes.One last board. Then we are finished.

Mini whiteboards, by segment

SegmentMWBTimeBoardsWhat to hold
WARM-UPretrieval3-5 minBOARDS UPQuestion up, boards up on the count. Everyone shows at once — a child who waits to see a neighbour's board has not retrieved anything.
I DOnone — they watch3-4 minboards downBoards DOWN and flat. This segment is watching, and a child writing is not watching. Say so once at the start of the year and then hold it.
WE DOprimary use5-6 minBOARDS UPOne step, then boards up. Do not let them run ahead to the answer — the point is that everybody is on the same step at the same time.
YOU DOon the sheet4-5 minboards downBoards down. This is the book's problems, worked where the work will be kept.
CLOSUREanswers displayed2-3 minboards downAnswers on the board, children check their own. Mark nothing here.
Watch for
Children stop while a composite is still on the list — 84 = 4 × 21 looks finished. The test is applied to EVERY factor, not to the feeling of being done.