Multiplication Tricks for 2 Digit Numbers: 14 × 16 in 2 Seconds

Step by step

1. Chinese mental-math classes: 2 seconds for this
   Kids in Chinese mental-math classes multiply numbers like these in about two seconds.
2. 14 rows × 16 seats · how many seats?
   A theater has fourteen rows, with sixteen seats in each row. How many seats are there?
3. 1 square = 1 seat · 14 rows, 16 across
   Each square is one seat: fourteen rows down, sixteen seats across.
4. Way 1: 14 = 10 + 4 · 16 = 10 + 6
   Way one is the school way. Cut fourteen into ten and four, and sixteen into ten and six.
5. Four boxes: 10 × 10 · 10 × 6 · 4 × 10 · 4 × 6
   That makes four boxes: ten times ten, ten times six, four times ten, and four times six.
6. 100 + 60 + 40 + 24 = 224
   One hundred, plus sixty, plus forty, plus twenty-four: two hundred twenty-four seats.
7. Trick: 14 + 6 = 20 → 200 · 4 × 6 = 24 → 224
   Now the two-second trick. Fourteen plus six is twenty. Times ten is two hundred. Then four times six is twenty-four. Two hundred twenty-four!
8. Why? This block: 4 rows of 10
   Why does it work? Look at this block: four rows of ten seats.
9. Turn it, slide it on → 10 rows of 20 = 200
   Turn it, and slide it onto the end of the top part. Now the top is ten rows of twenty seats: two hundred.
10. Corner left: 4 × 6 = 24
    The little corner left over is four times six: twenty-four. That's the whole trick!
11. Teen × teen: (14 + 6) × 10 + 4 × 6
    So for two teen numbers: add one number to the other's ones digit, times ten. Then add the two ones digits multiplied.
12. On a test: (10 + 4)(10 + 6) = 10 × 20 + 4 × 6 = 224
    On a test, write it like this. Split both numbers into ten plus ones, and multiply each part. Group the tens: ten times twenty. Then add four times six: two hundred twenty-four seats.