Halloween Math: Arrays and Multiplication, Grades 2–3

Teaching tips

Array habits that matter more than the theme

Most array errors come from a handful of misunderstandings. If you catch them early, the rest goes smoothly.

Agree on a convention. In this unit the first factor is the number of rows and the second is the number in each row. Whichever you pick, post it where students can see it.

Let students turn the array. Rotating 3 rows of 4 gives 4 rows of 3, and the total stays at 12. A 5 by 5 array looks the same after turning. Handling real counters makes this stick faster than any drawing.

Ask for every array of 12. Students usually find 3 by 4 and 2 by 6 and then stop. Prompt them for 1 by 12 and for the turned versions.

Link multiplication and division early. If 18 counters make 3 equal rows, then 18 divided by 3 is 6. Students who say "6 rows" have not yet looked at what the question counts.

Break big arrays into pieces. A 7 by 5 array is a 5 by 5 plus a 2 by 5, so 25 and 10. A common slip is breaking 8 by 4 into 5 rows and 4 rows; that makes nine rows, not eight, so the split has to be 5 and 3.

Common errors

Four misunderstandings to listen for

• Adding instead of multiplying: 3 + 4 for three plates of four cookies.
• Counting the picture: decorative illustrations are not counting models, only the labeled arrays are.
• Mixing up sharing and grouping when writing a division fact from a fact family.
• Trusting a word problem that cannot be solved because information is missing. Teach students to say what is missing.

The resources

The math unit and three practice products to pair with it

Haunted House Math comes first. The others are regular Grade 1–4 math practice that works before or after the arrays block.

Haunted House Math | Arrays, Fact Families & Multiplication | Grades 2–3

Grades 2–3Instant digital download

Math Warm-Up Bundle for Grades 1–4

Grades 1–4Instant digital download

Grade 3 Math Warm-Up Worksheets

Grade 3Instant digital download

Math Made Easy | Parent Guide & Practice Workbook | Grade 3

Grade 3Instant digital download

Planning the week

How six blocks can be spread across two weeks

1. Equal groupsBuild equal groups with counters and explain why adding the group size and the number of groups gives the wrong total.
2. Turn an arrayShow 3 × 4 and 4 × 3 together, and a 5 × 5 array that does not change when turned.
3. Find the missing factorFind all arrays of 12 and write division facts such as 18 ÷ 3 = 6.
4. A fact familyUse 2, 5 and 10 to write four facts. Test numbers that do not fit, like 2, 4 and 9, and check 4, 4 and 16, which has only two different facts.
5. Break apart a larger arraySplit 7 × 5 into 25 + 10 and 8 × 4 into 20 + 12.
6. Check a word problemOne window question in the unit cannot be solved because information is missing. Students find it and say what they would need.

What you get

What is in the ready-made unit

Each block takes 30 to 45 minutes, so you can fit one into a math lesson without losing the whole afternoon. Materials are pencils, two colors and 30 to 40 counters per pair. There is a learning check on page 27 and a "My math word bank" on page 28.

The teacher guide gives answers, teaching notes and SUPPORT, CORE and CHALLENGE suggestions. The prerequisite is counting and grouping; division is introduced through models, not as a rule to memorize.

Honest limits

Before you plan with it

Good to know

Frequently asked questions