/sci/ - Can someone explain this?

Name: Anonymous 2005-12-07 19:33

When you multiply 2^1990 by 5^1991 you get a product with 1991 digits. What is the sum of all of these digits?

Name: Anonymous 2005-12-07 20:30 (sage)

1990 pairs of twos and fives make 1990 tens, multiplied together.
multiplied by five, something that already had 1991 digits continues to have 1991 digits. It is 5(10^1990), and the sum of the digits is five.

Name: Anonymous 2005-12-07 20:32

It should be around 10000 I guess.

Name: Anonymous 2005-12-07 20:34

>>3
Duh, I failed miserably... I thought it was going to be hard to find out so I just did 5*1991

Name: Anonymous 2005-12-07 21:18

Wow, I should've realized that sooner. Thanks for clearing it up.

Name: Anonymous 2005-12-07 23:55

Take a university course in applied mathematics and computer programming.

Name: Anonymous 2005-12-08 0:20

5^1 } 5
5^2 = 25 } 7
5^3 = 125 } 8
5^4 = 625 } 13
5^5 = 3125 } 11
5^6 = 15625 } 19
5^7 = 78125 } 26
5^8 = 390625 } 25

1: Find pattern.
2: ???
3: Profit.

Name: Anonymous 2005-12-08 1:06 (sage)

>>7

no. you don't even need to find that pattern. In fact, it's really stupid. look at >>2.

Name: Anonymous 2005-12-08 14:41

>>6
Worst thing is, I did, but I didn't realize. Being really late in Europe might have helped me not realize, too.

Name: Anonymous 2005-12-08 16:59

5^1 } 5
5^2 = 25
5^8 = 390625 } 25

mite be somethin

Name: Anonymous 2005-12-19 0:17

Hey, every answer ends with 25.

Can someone explain this?

1 Name: Anonymous 2005-12-07 19:33

2 Name: Anonymous 2005-12-07 20:30 (sage)

3 Name: Anonymous 2005-12-07 20:32

4 Name: Anonymous 2005-12-07 20:34

5 Name: Anonymous 2005-12-07 21:18

6 Name: Anonymous 2005-12-07 23:55

7 Name: Anonymous 2005-12-08 0:20

8 Name: Anonymous 2005-12-08 1:06 (sage)

9 Name: Anonymous 2005-12-08 14:41

10 Name: Anonymous 2005-12-08 16:59

11 Name: Anonymous 2005-12-19 0:17