## Search found 8 matches

- Wed Dec 20, 2017 3:16 pm
- Forum: Junior Level
- Topic: so big series
- Replies:
**2** - Views:
**659**

### Re: so big series

We can divide all the numbers in 7 parts as (mod 7),7n,7n+1,7n+2,7n+3,7n+4,7n+5,7n+6. now see, 7n+1+7n+6=14n+7,7n+2+7n+5=14n+7 and 7n+3+7n+4=14n+7.so if we take those number which are 1(mod 7) we cannot take those which are 6(mod 7) and so on. there are floor of (400-1)/7 or 57 numbers from 1 to 400...

- Tue Dec 12, 2017 12:25 pm
- Forum: Higher Secondary Level
- Topic: A strange NUMBER THEORY Problem
- Replies:
**4** - Views:
**303**

### Re: A strange NUMBER THEORY Problem

But I have found it in Bigganchinta November 2017. You cannot tell that the question is wrong!

- Sun Dec 10, 2017 12:38 pm
- Forum: Higher Secondary Level
- Topic: A strange NUMBER THEORY Problem
- Replies:
**4** - Views:
**303**

### A strange NUMBER THEORY Problem

Because its hard for me so I am posting it here

The sum of three number is 12.Of them the sum of two number is 13.If the 3rd number is a natural number then what is it?

I have found it in Bigganchinta November 2017.Please help me to solve it.

The sum of three number is 12.Of them the sum of two number is 13.If the 3rd number is a natural number then what is it?

I have found it in Bigganchinta November 2017.Please help me to solve it.

- Sat Dec 09, 2017 12:14 pm
- Forum: Junior Level
- Topic: How many different ways
- Replies:
**1** - Views:
**132**

### Re: How many different ways

We will solve it in backwards, if we are i 7th floor we can come down to 6th,5th and 4th floor.There is chocolate in only 5th floor so we must come down to 5th floor.From 5th floor we can come down to 4th,3rd and 2nd floor as there is no chocolate in 4th floor we can come down to either 2nd or 3rd f...

- Fri Dec 08, 2017 8:55 pm
- Forum: Divisional Math Olympiad
- Topic: BdMO 2017 : Dhaka
- Replies:
**2** - Views:
**479**

### Re: BdMO 2017 : Dhaka

if we take 1as the first product 100000 can be written as product of 2 integers in 36

if 2 its 30

if 4 its 24

.

.

.

you can use this formula,

if X=P1a1*P2a2*P3a3...(P1a1 means p1 to the power a1and Pn is prime) then

the possible way to produce X into 2 integers is (a1+1)(a2+1)(a3+1)...

if 2 its 30

if 4 its 24

.

.

.

you can use this formula,

if X=P1a1*P2a2*P3a3...(P1a1 means p1 to the power a1and Pn is prime) then

the possible way to produce X into 2 integers is (a1+1)(a2+1)(a3+1)...

- Fri Dec 08, 2017 2:02 pm
- Forum: National Math Olympiad (BdMO)
- Topic: BDMO NATIONAL JUNIOR 2012/03
- Replies:
**4** - Views:
**406**

### Re: BDMO NATIONAL JUNIOR 2012/03

let x be the number of days in which it rained in morning and y be in the afternoon

then 16+x=13+y and x+y=11

by calculating these equations we find x=4 and y=7.so total day is 20

then 16+x=13+y and x+y=11

by calculating these equations we find x=4 and y=7.so total day is 20

- Fri Dec 08, 2017 1:56 pm
- Forum: National Math Olympiad (BdMO)
- Topic: BDMO NATIONAL JUNIOR 2012/03
- Replies:
**4** - Views:
**406**

### Re: BDMO NATIONAL JUNIOR 2012/03

is it 20 days?

- Sun Oct 22, 2017 6:01 pm
- Forum: Junior Level
- Topic: Find $x$
- Replies:
**4** - Views:
**442**

### Re: Find $x$

x(x-3) = -5 = 6 (mod 11)

by testing the factors of 6 we get that x = 7 (mod 11)

by testing the factors of 6 we get that x = 7 (mod 11)