why is it that when the number 9 is multiplied the answer adds up to number 9
2006-09-14 09:16:55 · 18 answers · asked by mickeok 1 in Education & Reference ➔ Teaching
Only up to 10 x 9.
2006-09-14 09:17:54 · answer #1 · answered by Anonymous · 0⤊ 0⤋
That is because we use base 10 numbers.
If the base was 9 where the only digits were 0-8 they would add up to 8. 3*8=26 6+2=8
If the base was 5 where the only digits were 0-4 they would add up to 4. 3*4=22 2+2=4
2006-09-14 09:31:34 · answer #2 · answered by Barkley Hound 7 · 0⤊ 0⤋
Unsure, but did you know, for all the multiples under 10, if you look at your hands palms up, then count from your left thumb the number you are multiplying by and bend that finger...so if you were doing 5 x 9 you would bend the little finger on your left hand to get your answer. Now, look down at your hands, so to the left of the bent finger is the tens - 40, and on the right is the units - 5.
2006-09-17 09:52:48 · answer #3 · answered by Rachael B 1 · 0⤊ 0⤋
I don't know the reason for it, but its a good way of checking if a number is divisable by 9 - basically if the sum of the digits of the answer is in the 9 times table it is
eg. 459
4+5+9=18 18 is in the 9 times table so is divisable by 9.
There is the same test for the 3x table - add the sum of the digits, if its divisable by 3 the number is divisable by 3.
6x - if the divisable by 3 test works and its even, then divisable by 6!
There are tricks like that for most of the tables!
2006-09-16 08:30:20 · answer #4 · answered by Beth 2 · 1⤊ 0⤋
why does 2 + 2 = 4?
2006-09-14 09:19:06 · answer #5 · answered by Derek 4 · 0⤊ 0⤋
it does work for 10x9 and 11x9 . Just add the answer numbers together 10x9=90 9+0=9 and11x9=99 9+9=18 1+8=9 In fact it works for any multiple of 9 if you just keep adding the numbers of the answer together.
2006-09-14 09:28:06 · answer #6 · answered by ruth471711 2 · 2⤊ 0⤋
11x9=99
9+9=18
1+8=9. so it does work with 11x9 in a roundabout way
12x9=108
1+0+8= 9
13x9=117
1+1+7=9
14x9=126
1+2+6=9
2006-09-14 09:30:30 · answer #7 · answered by Steve K 4 · 0⤊ 0⤋
The only exception is 11 x 9.
2006-09-14 09:19:33 · answer #8 · answered by Anonymous · 0⤊ 0⤋
It's only up to 10 x 9 this is because you only have ten fingers. You can do the 9 times table on your hand, put down the thumb and you have nine, next put down your index finger and you have 18, put down your middle finger and you have 27 and so on and so on. I learnt this at school and never forgot.
2006-09-14 09:32:55 · answer #9 · answered by XhappytalkX 3 · 0⤊ 0⤋
what a stupid question it just is like why is 2+2=4 and why is everything what it is like why is the world caled the world and why is a cow called a cow and why is blue blue and not green Etc
2006-09-14 09:26:14 · answer #10 · answered by michaelizdabest 3 · 0⤊ 0⤋