Learning Objectives
- 01
Multiply fluently by 10, 100, 1000.
- 02
Decompose a multi-digit number and multiply each place value.
Multiplication Foundations
Multiplying by powers of 10 and decomposing multi-digit numbers.
Topics
Multiplying by 10/100/1000Mental decomposition
Worked Examples
432 × 3=1296
Left-to-right 3×1 (Benjamin): hundreds, tens, units — each piece, then add.
- 01
400 × 3 = 1200
Hundreds first.
- 02
30 × 3 = 90
Tens next.
- 03
2 × 3 = 6
Then units.
- 04
1200 + 90 + 6 = 1296
Add as you go, left-to-right — say each running total aloud.
- →
= 1296
528 × 4=2112
Left-to-right 3×1 (Benjamin): hundreds, tens, units — each piece, then add.
- 01
500 × 4 = 2000
Hundreds first.
- 02
20 × 4 = 80
Tens next.
- 03
8 × 4 = 32
Then units.
- 04
2000 + 80 + 32 = 2112
Add as you go, left-to-right — say each running total aloud.
- →
= 2112
23 × 4=92
Left-to-right multiplication (Benjamin): break the 2-digit number into tens + units, multiply each, add.
- 01
20 × 4 = 80
Tens first — biggest piece always goes first to keep the running total anchored.
- 02
3 × 4 = 12
Now the units piece.
- 03
80 + 12 = 92
Add the two partial products — left-to-right addition.
- →
= 92
Benjamin, Secrets of Mental Math — distribute by place
56 × 7=392
Left-to-right multiplication (Benjamin): break the 2-digit number into tens + units, multiply each, add.
- 01
50 × 7 = 350
Tens first — biggest piece always goes first to keep the running total anchored.
- 02
6 × 7 = 42
Now the units piece.
- 03
350 + 42 = 392
Add the two partial products — left-to-right addition.
- →
= 392
Benjamin, Secrets of Mental Math — distribute by place
67 × 3=201
Left-to-right multiplication (Benjamin): break the 2-digit number into tens + units, multiply each, add.
- 01
60 × 3 = 180
Tens first — biggest piece always goes first to keep the running total anchored.
- 02
7 × 3 = 21
Now the units piece.
- 03
180 + 21 = 201
Add the two partial products — left-to-right addition.
- →
= 201
Benjamin, Secrets of Mental Math — distribute by place
Talking Points
- •Master tables 2–10 cold, then push through 11–19.
- •Always say the running total aloud.
Week 1 · Fundamentals
Mental Math Fundamentals & Basic Operations
- →Develop left-to-right calculation habits
- →Strengthen multiplication table mastery
- →Learn fundamental mental shortcuts
Sample Problems · Week 1
One simple and one intermediate problem to preview the week.
Simple · Day 1
57 + 38=95
Intermediate · Day 3
314 × 11=3454