Divisibility Rules!

To find if some number X is divisible by prime numbers, test the number by using the information in the table below.

By 2	If the last digit divisible by two, then X is too
By 3	If the sum of the digits of the number X is divisible by three, then X is too
By 5	If the last digit is 5 or 0, then X is divisible by 5
By 7	The last digit of X times 2 and subtract it from X without its last digit. For instance, if the number X you are testing is 345678, you would subtract 16 from 34567. Repeat this procedure until you get a number that you know for sure is or is not divisible by 7.
By 11	What you do here is to make two sums of digits and subtract them. The first sum is the sum of the first, third, fifth, seventh, etc. digits and the other sum is the sum of the second, fourth, sixth, eighth, etc. digits. If, when you subtract the sums from each other, the difference is divisible by 11, then the number X is too
By 13	The last digit of X times 4 and add it from X without its last digit. For instance, if the number X you are testing is 345678, you would add 32 to 34567. Repeat this procedure until you get a number that you know for sure is or is not divisible by 13.
By 17	The last digit of X times 5 and subtract it from X without its last digit. For instance, if the number X you are testing is 345678, you would subtract 40 from 34567. Repeat this procedure until you get a number that you know for sure is or is not divisible by 17.
By 19	The last digit of X times 2 and add it from X without its last digit. For instance, if the number X you are testing is 345678, you would add 16 to 34567. Repeat this procedure until you get a number that you know for sure is or is not divisible by 19.
By 23	The last digit of X times 7 and add it from X without its last digit. For instance, if the number X you are testing is 345678, you would add 52 to 34567. Repeat this procedure until you get a number that you know for sure is or is not divisible by 23.
By 29	The last digit of X times 3 and add it from X without its last digit. For instance, if the number X you are testing is 345678, you would add 24 to 34567. Repeat this procedure until you get a number that you know for sure is or is not divisible by 29.
By 31	The last digit of X times 3 and substract it from X without its last digit. For instance, if the number X you are testing is 345678, you would substract 24 to 34567. Repeat this procedure until you get a number that you know for sure is or is not divisible by 31.
By 37	The last digit of X times 11 and subtract it from X without its last digit. For instance, if the number X you are testing is 345678, you would subtract 88 from 34567. Repeat this procedure until you get a number that you know for sure is or is not divisible by 37.
By 41	The last digit of X times 4 and substract it from X without its last digit. For instance, if the number X you are testing is 345678, you would substract 32 to 34567. Repeat this procedure until you get a number that you know for sure is or is not divisible by 41.
By 43	The last digit of X times 11 and add it from X without its last digit. For instance, if the number X you are testing is 345678, you would add 88 to 34567. Repeat this procedure until you get a number that you know for sure is or is not divisible by 43.
By 47	The last digit of X times 14 and subtract it from X without its last digit. For instance, if the number X you are testing is 345678, you would subtract 112 from 34567. Repeat this procedure until you get a number that you know for sure is or is not divisible by 47.
By 53	The last digit of X times 16 and add it from X without its last digit. For instance, if the number X you are testing is 345678, you would add 128 to 34567. Repeat this procedure until you get a number that you know for sure is or is not divisible by 53.
By 59	The last digit of X tmes 6 and add it from X without its last digit. For instance, if the number X you are testing is 345678, you would add 54 to 34567. Repeat this procedure until you get a number that you know for sure is or is not divisible by 59.
By 61	The last digit of X times 6 and substract it from X without its last digit. For instance, if the number X you are testing is 345678, you would substract 48 to 34567. Repeat this procedure until you get a number that you know for sure is or is not divisible by 61.
By 67	The last digit of X times 20 and subtract it from X without its last digit. For instance, if the number X you are testing is 345678, you would subtract 160 from 34567. Repeat this procedure until you get a number that you know for sure is or is not divisible by 67.
By 71	The last digit of X times 7 and substract it from X without its last digit. For instance, if the number X you are testing is 345678, you would substract 56 to 34567. Repeat this procedure until you get a number that you know for sure is or is not divisible by 71.
By 73	The last digit of X times 22 and add it from X without its last digit. For instance, if the number X you are testing is 345678, you would add 176 to 34567. Repeat this procedure until you get a number that you know for sure is or is not divisible by 73.
By 79	The last digit of X tmes 8 and add it from X without its last digit. For instance, if the number X you are testing is 345678, you would add 64 to 34567. Repeat this procedure until you get a number that you know for sure is or is not divisible by 79.
By 83	The last digit of X times 7 and add it from X without its last digit. For instance, if the number X you are testing is345678, you would add 52 to 34567. Repeat this procedure until you get a number that you know for sure is or is not divisible by 83.
By 89	The last digit of X tmes 9 and add it from X without its last digit. For instance, if the number X you are testing is 345678, you would add 72 to 34567. Repeat this procedure until you get a number that you know for sure is or is not divisible by 89.
By 97	The last digit of X times 29 and subtract it from X without its last digit. For instance, if the number X you are testing is 345678, you would subtract 232 from 34567. Repeat this procedure until you get a number that you know for sure is or is not divisible by 97.

Teka-Teki Logika Sederhana 1

 Pertanyaan:
Tanpa menggunakan operasi penjumlahan, pengurangan, perkalian, dan pembagian, susunlah 6 angka 9 sehingga mempunyai nilai 100.
Lihat Jawaban:

Teka-Teki Logika Sederhana 2

Pertanyaan:
Jika diperlukan waktu satu menit untuk merebus satu telur, berapa waktu yang diperlukan untuk merebus sepuluh telur?
Lihat Jawaban:

Misteri Bilangan Lubang Hitam: 123

Dalam astronomi dan fisika, kita mengenal adanya suatu fenomena alam yang sangat menarik yaitu lubang hitam (black hole). Lubang hitam adalah suatu entitas yang memiliki medan gravitasi yang sangat kuat sehingga setiap benda yang telah jatuh di wilayah horizon peristiwa (daerah di sekitar inti lubang hitam), tidak akan bisa kabur lagi. Bahkan radiasi elektromagnetik seperti cahaya pun tidak dapat melarikan diri, akibatnya lubang hitam menjadi “tidak kelihatan”. Ternyata, dalam matematika juga ada fenomena unik yang mirip dengan fenomena lubang hitam yaitu bilangan lubang hitam. Bagaimana sebenarnya bilangan lubang hitam itu? Mari kita bermain-main sebentar dengan angka.
Coba pilih sesuka hati Anda sebuah bilangan asli (bilangan mulai dari 1 sampai tak hingga). Sebagai contoh, katakanlah 141.985. Kemudian hitunglah jumlah digit genap, digit ganjil, dan total digit bilangan tersebut. Dalam kasus ini, kita dapatkan 2 (dua buah digit genap), 4 (empat buah digit ganjil), dan 6 (enam adalah jumlah total digit).

Euclid

Euclid yang tinggal disekitar 300BC dianggap sebagai bapak Geometri dan opus magnumnya elements. Tidak banyak orang yang beruntung memperoleh kemasyuran yang abadi seperti euclid, ahli ilmu ukur yunani yang besar. Meskipun semasa hidupnya tokoh-tokoh seperti Napoleon , Martin Luther, Alexander yang Agung, jauh lebih terkenal dibandingkan Euclid tetapi dalam jangka panjang ketenarannya mungkin  mengungguli semua mereka yang disebut itu.  Selain kemasyhurannya hampir tidak ada keterangan terperinci mengenai kehidupan euclid yang bisa diketahui. Misalnya kita tahu dia pernah aktif sebagai guru di Iskandariah, Mesir, disekitar tahun 300SM.  Tetapi kapan dia lahir kapan dia wafat betul-betul gelap.  Bahkan kita tidak tahu di benua apa dan di kota apa dia dilahirkan, meski dia menulis beberapa buku yang umumnya pada topik Geometri atau Teori Nomor. Ada juga lima karya-karya yang sayangnya telah hilang sepanjang sejarah. Kedudukannya dalam sejarah terutama terletak pada textbooknya yang hebat mengenai ilmu ukur yang bernama The elements . Elements, adalah salah satu karya matematika terbesar dalam sejarah, dengan perusahaan yang digunakan dalam pendidikan sampai abad ke-20.

Arti penting buku The Elements tidaklah tetletak pada rumus-rumus pribadi yang dilontarkan karena hampir semua teori sudah dibuktikan. Namun sumbangan Euclid

Ilusi matematika??

Dalam kehidupan sehari-hari, terkadang kita mengalami ilusi maupun hal-hal aneh. Gambar-gambar yang unik dan menarik bisa jadi hanya sebuah ilusi optik. Ternyata tidak hanya dalam kehidupan nyata saja, dalam matematika juga ada ilusi. Karena menggunakan unsur-unsur yang identik dengan matematika, maka kebanyakan menyebutnya dengan ilusi optik matematika. Seperti apa contoh gambar matematika yang membingungkan tersebut? Inilah beberapa contohnya.

Sejajarkah garis horisontalnya?

Ingin Pintar Matematika,

• Silahkan Setrum Kepala Anda

Disetrum ??? Wow,, kedengerannya extrim banget kan. Ini sudah diteliti lo.. Buat lebih jelasnya,disimak ya..

Ternyata dengan mengalirkan sedikit arus listrik ke otak selama 15 menit, kemampuan orang dalam matematika bisa meningkat. Para ilmuwan di University of Oxford, Inggris, sudah berhasil melakukan itu dan membuat kemampuan matematika seseorang bertahan selama 6 bulan.

Para ilmuwan menggunakan teknik stimulasi menggunakan arus listrik yang disalurkan langsung lewat tempurung untuk mengalirkan listrik ke bagian otak yang biasa digunakan untuk memproses angka (parietal lobe).

Partisipan diminta untuk mempelajari simbol-simbol yang mewakili angka. Kemudian, selama mereka menerima arus listrik, mereka diminta mengorganisasi angka-angka tersebut. Partisipan yang diberi stimulasi memiliki kemampuan yang lebih baik dalam menyelesaikan tugas ketimbang partisipan tanpa stimulasi. Hebatnya, ketika uji coba dilakukan 6 bulan kemudian, kemampuan itu masih ada.

Para ilmuwan mengaku akan melakukan penelitian lagi. “Penelitian berikutnya akan melibatkan orang-orang yang lemah dalam bidang matematika,” jelas ilmuwan dari University of Oxford. Mereka juga mengaku penelitian ini akan membantu 20 persen orang yang memiliki kemampuan matematika di bawah rata-rata dan mungkin pula dapat diterapkan di bidang selain matematika.

Anda ingin pintar,,,, mari qta mencoba bersama sama ….. hehe