Find the Number of PrimeNumbers

[rakeen]

I found this in BdMO Div(don't remember the year). It says, A set has 20 'cromic dhonattok purnaa shonkha'. They all are greater than 50. How many Prime Numbers there will be in that set?

$Note:$ hint first.

[AntiviruShahriar]

প্রত্যেক $20$ টি সংখ্যার মধ্যে $10$ টি জোড়। বাকি $10$ টির মধ্যে প্রতি $4$ টি বিজোড়ের $1$ টি $3$ দ্বারা বিভাজ্য। $10$/$4$=$2.5$.তাই আমরা $3$ টির জন্য $3$ টি আর $2$ টির জন্য $2$ টি বিয়োগ দিব।
$20$ টি এর মধ্যে $5$ দ্বারা বিভাজ্য আছে $3$ টি, এর মধ্যে $1$ টি $3$,$5$ উভয় দ্বারা বিভাজ্য। আর এক্তা $7$ দ্বারা বিভাজ্য
অতএব, বাকি থাকে $20$-$10$-$3$ or $2$-$3$+$1$-$1$=$5$ or $4$ টি
I am not sure about this solution....i just guessed it........

[AntiviruShahriar]

I found this in BdMO Div(don't remember the year). It says, A set has 20 'cromic dhonattok purnaa shonkha'. They all are greater than 50. How many Prime Numbers there will be in that set?

$Note:$ hint first.

sorry আমি hidden করার নিয়ম জানি না। নিচে না তাকিয়ে কর।

[rakeen]

your technique is quite interesting. ektu matha khatalei hoy.

thnx

[Muhiminul Maruf]

ansta ki shahriarer ta thik ase????????

[AntiviruShahriar]

rakeen--welxxxxxx.maruf--jani na just guess korsii..tui r 1ta bair korte parle post kor...dekhi thikase naaki

[Dipan]

The ans should be 3 if there is no twin prime.

[rakeen]

@Anti tomar solution ta thik moto bujhi nai. But it helped me a lot.
@Dipan mine is 6. bcoz the question says "possible highest" number of prime.

Of the 10 odd numbers there are 3/4 such numbers that are divisible by 3. But according to question we have to consider, there are 3 such number which are divisible by 3. Again, of the 10 odd numbers there are 2 such numbers that are divisible by 5.But, of the 2(wchich are divisible by 5) numbers, one or two is divisible by 3. But according to question we have to consider, of them only one number is divisible by 3(which is also divisible by 5). So, of the 10 odd numbers there are 3+1=4 numbers which are divisible either by 3 or 5. So we have 10-4=6 such numbers who are not divisible by 2,3,4,5,6,8,9.(I have not consider 7). That means 6 of them are prime

[AntiviruShahriar]

The ans should be 3 if there is no twin prime.

proof???????

[AntiviruShahriar]

@Anti tomar solution ta thik moto bujhi nai. But it helped me a lot.
@Dipan mine is 6. bcoz the question says "possible highest" number of prime.

Of the 10 odd numbers there are 3/4 such numbers that are divisible by 3. But according to question we have to consider, there are 3 such number which are divisible by 3. Again, of the 10 odd numbers there are 2 such numbers that are divisible by 5.But, of the 2(wchich are divisible by 5) numbers, one or two is divisible by 3. But according to question we have to consider, of them only one number is divisible by 3(which is also divisible by 5). So, of the 10 odd numbers there are 3+1=4 numbers which are divisible either by 3 or 5. So we have 10-4=6 such numbers who are not divisible by 2,3,4,5,6,8,9.(I have not consider 7). That means 6 of them are prime

majhe majhe ami nijeo bujhi na....6 ta prime ase emon example dao to......tomar qs ta poro tumi highest bolso koi?????tobee aj k amar solution nia boshsilam bt oita te vul o thakte parre jokhon prime number 20 tar moddhey 3 ta hoy..j mon 521 to 540 te 3 ta ase.........