Prime Numbers - Magic Trick!! - Part 1 | Fun Math | Don't Memorise

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[InfinityLearn_NEET]

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[GamingAmit]

All time favourite learning channel thank you for clear my all doubts 😊

[aasmizope]

Thank you so much...It was really helpful I had my math exam on this topic today and I finished really quick and correct due to these tricks...thank you so much...love from mumbai

[sujatasharma]

I got to know about this trick 8 years ago. And the proof involves Euclid's division lemma when I did it myself during the grade I studied that lemma. I felt quite proud of myself then.

[abdulganifoysal]

What about 49?
49 square is 2401. If we subtract 1, we get 2400 which is divided by 24.
But 49 has more than 2 variables, its 1, 49, 7. Then how 49 is a prime number?

[rehmanzabeer]

Please make a video on Surface Tension.. 😊

[maddybmm]

Out of three consecutive numbers p-1, p, p+1 one should divisible by 3.
Also p−1 is divisible by 2 and p+1 is divisible by 4.
Therefore since either p−1 or p+1 is divisible by 4 and the other 2, their product is divisible by 8. Therefore (p−1)(p+1) is divisible by 8 and 3, and therefore 2*4*3=24.

This means for any prime p>3,  p2−1=(p−1)(p+1) is divisible by 24.

[stevensmith]

Yes, this trick is works for prime number, but it also gives reminder as 0 for some non prime numbers too such as 143,

In exam I thought it was prime becuase of that, and made a huge mistake!

[littlelilly]

10th class lemma which i never applied ! Thanks for this)

[neochepete]

Got everything wrong on my math quiz 😢

[Bk-piqf]

This trick is each prime number's square +1 is divisible by 24
But not all numbers which is divisible by 24 is not a prime number

So if a number's square+1 is not divisible by 24 it is not a prime number

[MonirulIslam-dllf]

what about 91? is it prime number, ? as we can divide this with 24!

[radheshyambansal]

and it was easy trick







from another number u make vdo trick.

[munnurushravani]

7^2 = 49
49-1 = 48
48 is divisible by 24
but 49 is not a prime number

[BinodKumar-hush]

Answer is simple
Every prime number exist in 6 k± 1 form so,
p²-1 =12k(3k±1) which is divisible by 24

[ShadheenIslam]

91 is Not a prime but 91^2-1=345 (reminder 0 )

[Nebulous_o]

It works with 7. We all know how special 7 is.

[Jagwan-uk]

what about 169 ? as per your formula its prime number

[rahulkambala]

391 is showing as prime number by using this trick

[quickdeliverymaths]

All odd prime number's square minus 1 are divisible by 8.
3²-1=8
5²-1=24
7²-1=48 etc.