Search found 8 matches

by thczarif
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...
by thczarif
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! :geek:
by thczarif
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.
by thczarif
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...
by thczarif
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
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.
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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)...
by thczarif
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
by thczarif
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?
by thczarif
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) :D