Here is a very nifty way for writing multiplication table of numbers ending in 9.
Let’s say you want to write multiplication table of 29.
Notice that the ten’s digit is 2. The next higher number to 2 is 3.
So, the first part of each row will be previous row’s ten’s digit plus 3. And the last part of each row will be complement of that multiplier i.e. the unit Place digit will be 9, 8, 7, 6, 5, 4, 3, 2, 1 & 0.
29 × 2 = (2+3) / 8 = 58
29 × 3 = (5+3) / 7 = 87
29 × 4 = (8+3) / 6 = 116
29 × 4 = (8+3) / 6 = 116
29 × 5 = (11+3)/ 5 = 145
29 × 6 = (14+3)/ 4 = 174
29 × 7 = (17+3)/ 3 = 203
29 × 8 = (20+3)/ 2 = 232
29 × 9 = (23+3)/ 1 = 261
29 × 10 = (26+3)/ 0 = 290
See the pattern? We can write any table, with digit 9 at unit place, by using this trick.
Another Example: Table of 59 (say)
The ten’s digit here is 5. The next higher number to 5 is 6.
So, the first part of each row will be 6 plus previous answer’s ten’s digit. The last part of each row will be 9, 8, 7, 6, 5, 4, 3, 2, 1 & 0.
59 × 1 = 5 / 9 = 59
59 × 2 = (5+6) / 8 = 118
59 × 3 = (11+6) / 7 = 177
59 × 4 = (17+6) / 6 = 236
59 × 5 = (23+6)/ 5 = 295
59 × 6 = (29+6)/ 4 = 354
59 × 7 = (35+6)/ 3 = 413
59 × 8 = (41+6)/ 2 = 472
59 × 9 = (47+6)/ 1 = 531
59 × 10 = (53+6)/ 0 = 590
We can't use it for 19?
ReplyDeleteYou’ve got some interesting points in this article. I would have never considered any of these if I didn’t come across this. Thanks!. Multiplication chart printable
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