Let me guess ur birthday !

Step 1) Have them take the month number from their birthday: January = 1, Feb = 2 etc.
Step 2) Multiply that by 5
Step 3) Then add 6
Step 4) Then multiply that total by four
Step 5) Then add 9
Step 6) Then multiply this total by 5 once again
Step 7) Finally, have them add to that total the day they were born on. If they were born on the 18th, they add 18, etc.

Have them give you the total. In your head, subtract 165, and you will have the month and day they were born on!

How It Works: Let M be the month number and D will be the day number. After the seven steps the expression for their calculation is:

5 (4 (5 M + 6 ) + 9 ) + D = 100 M + D + 165

Thus, if you subtract off the 165, what will remain will be the month in hundreds plus the day!

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Versi bm:

k..Skrg ni katakan aku nak try teka tarikh lahir korang...then aku suruh kurang buat kiraan dibawah;

langkah1:ambil no. bulan yg korang lahir (cth:lahir bulan 5)
langkah2:darab no. tadi dengan 5 (5*5=25)
langkah3:kemudian tambah 6 (25+6=31)
langkah4:kemudian jumlah tadi darab 4 (31*4=124)
langkah5:jumlah tu plak tambah 9 (124+9=133)
langkah6:darab jumlah tadi ngan 5 (133*5=665)
langkah7:kmudian tambah jumlah akhir tadi dengan haribulan korang lahir.katakan lahir pada 12 haribulan 5,perlu tambah 12 (665+12=677)

lepas korang kira diatas,barulah aku tanya nilai angka akhir yang korang dapat.lepas tu macam contoh yg aku buat korang akan jawab 677...dengan muke machonyerr,dalam kpala otak aku,aku trus congak nilai akhir tu tolak 165 iaitu 677-165=512....dan dengan machonyerr skali lagi aku pun bersuara,korang lahir 12 hb 5 kan ?512 tu 5 tu ialah bulan dan 12 ialah hari....selepas korang tolak 165,angka yg datang dulu ialah angka menunjukkan bulan kelahiran dan angka kemudian menunjukkan bilangan hari...katakan korang dapat angka 1231 selepas tolak 165,bermakna dia lahir 31 hb 12....dats all...gud luck!