| Blogs > kdog3683 |
|
kdog3683
United States916 Posts
729 = + Show Spoiler + 3^6 2048 = + Show Spoiler + 2^11 How would you do this quickly? 15seconds, no calculator. What is the process you go through? I divide by small #s, 2,3,4,5... If 2 fits, i divide by 2 again, else I try 3. Else, 4, etc, but this is slow.   | ||
|
Durak
Canada3685 Posts
| ||
|
Abydos1
United States832 Posts
On February 02 2009 11:16 kdog3683 wrote: Simplify to the form a^b LOL, thats not simplifying it. | ||
|
naonao
United States847 Posts
but otherwise i do a branch thingy like for instance 144 would be like 144 / \ 12 12 / \ / \ 3 4 3 4 | / \ | / \ 3 2 2 3 2 2 Also some tips to know when numbers are divisible by others: 2: number is even 3: sum of the digits is a multiple of 3 4: last two digits are divisible by 4 5: ends in 0 or 5 6: even and the digits add up to a multiple of 3 7: NOTHING 8: last 3 digits are divisible by 8 9: sum of the digits is a multiple of 9 | ||
|
paper
13196 Posts
but i think there are some tricks for some numbers | ||
|
Malongo
Chile3472 Posts
| ||
|
foppa
Canada451 Posts
| ||
micronesia
United States24758 Posts
| ||
Plexa
Aotearoa39261 Posts
 although there is a method to test if a number is dividable by 7.. its just so complicated that its quicker to just brute force it haha | ||
|
Pwert
United States59 Posts
On February 02 2009 11:26 naonao wrote: Thats memorization. powers of 2 and powers of 3. but otherwise i do a branch thingy like for instance 144 would be like 144 / \ 12 12 / \ / \ 3 4 3 4 | / \ | / \ 3 2 2 3 2 2 Also some tips to know when numbers are divisible by others: 2: number is even 3: sum of the digits is a multiple of 3 4: last two digits are divisible by 4 5: ends in 0 or 5 6: even and the digits add up to a multiple of 3 7: NOTHING 8: last 3 digits are divisible by 8 9: sum of the digits is a multiple of 9 Actually, I know of this interesting (but time consuming) way of finding out if a number is divisible by 7. You take the digit farthest to the right, double it, and subtract it from the original number over and over until you have a number from 9 to negative 9. If it turns out to be 7, 0, or negative 7 then the number is divisible by 7. Example: 182 becomes (18 - 2) which equals 14. 14 becomes (1 - 8) which equals negative 7. 182 is divisible by 7. Example: 6881 becomes (688 - 2) which equals 686. 686 becomes (68 - 12) which equals 56. 56 becomes (5 - 12) which equals negative 7. 6881 is divisible by 7 Example: 531 becomes (53 - 2) which equals 51. 51 becomes (5 - 2) which equals 3. 531 is not divisible by 7. | ||
| ||
|
|
WardiTV Team League
OSC
Replay Cast
KCM Race Survival
WardiTV Team League
Korean StarCraft League
RSL Revival
Maru vs Zoun
Cure vs ByuN
uThermal 2v2 Circuit
BSL
RSL Revival
herO vs MaxPax
Rogue vs TriGGeR
[ Show More ] |
|
|
EPT
