Timed Multiplication Challenge

Left-to-right 3×1 (Benjamin): hundreds, tens, units — each piece, then add.

1. 01

   800 × 3 = 2400

   Hundreds first.

2. 02

   80 × 3 = 240

   Tens next.

3. 03

   8 × 3 = 24

   Then units.

4. 04

   2400 + 240 + 24 = 2664

   Add as you go, left-to-right — say each running total aloud.

5. →

   = 2664

Benjamin, Secrets of Mental Math — distribute left-to-right

Left-to-right 3×1 (Benjamin): hundreds, tens, units — each piece, then add.

1. 01

   200 × 8 = 1600

   Hundreds first.

2. 02

   50 × 8 = 400

   Tens next.

3. 03

   3 × 8 = 24

   Then units.

4. 04

   1600 + 400 + 24 = 2024

   Add as you go, left-to-right — say each running total aloud.

5. →

   = 2024

Benjamin, Secrets of Mental Math — distribute left-to-right

Left-to-right 3×1 (Benjamin): hundreds, tens, units — each piece, then add.

1. 01

   300 × 6 = 1800

   Hundreds first.

2. 02

   60 × 6 = 360

   Tens next.

3. 03

   2 × 6 = 12

   Then units.

4. 04

   1800 + 360 + 12 = 2172

   Add as you go, left-to-right — say each running total aloud.

5. →

   = 2172

Benjamin, Secrets of Mental Math — distribute left-to-right

×9 shortcut (Benjamin): use (n × 10) − n.

1. 01

   831 × 10 = 8310

   Multiplying by 10 just shifts a zero on the end.

2. 02

   8310 − 831 = 7479

   Subtract one copy of 831, because 9 = 10 − 1.

3. →

   = 7479

Benjamin, Secrets of Mental Math — distribute left-to-right

Left-to-right 3×1 (Benjamin): hundreds, tens, units — each piece, then add.

1. 01

   800 × 6 = 4800

   Hundreds first.

2. 02

   50 × 6 = 300

   Tens next.

3. 03

   8 × 6 = 48

   Then units.

4. 04

   4800 + 300 + 48 = 5148

   Add as you go, left-to-right — say each running total aloud.

5. →

   = 5148

Benjamin, Secrets of Mental Math — distribute left-to-right