## Search found 3 matches

- Thu Jan 17, 2019 1:20 pm
- Forum: Divisional Math Olympiad
- Topic: Bdmo regional 2018 set 1 Higher Secondary 8
- Replies:
**1** - Views:
**211**

### Re: Bdmo regional 2018 set 1 Higher Secondary 8

There were $n$ couples that means total $2n$ persons. If each person would shake hands with every other person, the total number of hand shakes would be $^{2n}C_2$. But the total number of hand shakes is $^{2n}C_2 - n$. Because $n$ couple didn't shake hand with their spouse. Now, $^{2n}C_2 - n = 312...

- Thu Jan 17, 2019 12:49 pm
- Forum: Divisional Math Olympiad
- Topic: 2018 Regional Set $2$ Higher Secondary $P6$
- Replies:
**2** - Views:
**289**

### Re: 2018 Regional Set $2$ Higher Secondary $P6$

$65^{2016} - 65^{2015} = 65^{2015}(65-1) = 65^{2015}\times64$ Now let's convert $64$ into Binary. $(64)_2 = 1000000$. Notice that there are $6$ $zero$s at the end of the number. That means if we multiply any number with that number, we will get $6$ $zero$s at end. Let's determine the $7^{th}$ number...

- Tue Jan 15, 2019 12:29 am
- Forum: Higher Secondary Level
- Topic: Intresting Factorial!
- Replies:
**2** - Views:
**331**

### Re: Intresting Factorial!

The number is $25$. First we have to think how $0$ produces at last position. It must be done by multiplying by $10$. So we need to determine the factorial of lowest number that produces $6$, 10s... $25! = 1\times2\times3\times4\times... ...\times24\times25$ Here i. $2\times5 = 10$ ii. $10 = 1\times...