Násobení je matematická operace, která může být reprezentována jako součet identických členů.

Obsah

Obecný princip násobení

Například, a ⋅ b (čteno jako „a krát b“) znamená, že sčítáme členy a, jejichž počet se rovná b. Výsledek násobení se nazývá součin.

Jak se rychle a snadno naučit násobilku

příklady:

  • 2 ⋅ 6 = 2 + 2 + 2 + 2 + 2 + 2 = 12

    (šest krát dva)

  • 5 ⋅ 4 = 5 + 5 + 5 + 5 = 20

    (čtyři krát pět)

  • 3 ⋅ 8 = 3 + 3 + 3 + 3 + 3 + 3 + 3 + 3 = 24

    (osm krát tři)

Jak víme, z permutace míst faktorů se součin nemění. U výše uvedených příkladů se ukazuje:

  • 6 ⋅ 2 = 6 + 6 = 12

    (dvakrát šest)

  • 4 ⋅ 5 = 4 + 4 + 4 + 4 + 4 = 20

    (pět krát čtyři)

  • 8 ⋅ 3 = 8 + 8 + 8 = 24

    (třikrát osm)

Praktické výhody

Díky násobení můžete výrazně snížit počet z celkového počtu položek stejného typu atd. Pokud máme například 7 balíčků, z nichž každý obsahuje 5 per, pak celkový počet per zjistíme vynásobením těchto dvě čísla:

5 ⋅ 7 = 5 + 5 + 5 + 5 + 5 + 5 + 5 = 35

(pět per sedmkrát)

Vynásobte 0

Výsledek je vždy nula.

  • 0 ⋅ 0 = 0
  • 1 ⋅ 0 = 0 ⋅ 1 = 0
  • 2 ⋅ 0 = 0 ⋅ 2 = 0 + 0 = 0
  • 3 ⋅ 0 = 0 ⋅ 3 = 0 + 0 + 0 = 0
  • 4 ⋅ 0 = 0 ⋅ 4 = 0 + 0 + 0 + 0 = 0
  • 5 ⋅ 0 = 0 ⋅ 5 = 0 + 0 + 0 + 0 + 0 = 0
  • 6 ⋅ 0 = 0 ⋅ 6 = 0 + 0 + 0 + 0 + 0 + 0 = 0
  • 7 ⋅ 0 = 0 ⋅ 7 = 0 + 0 + 0 + 0 + 0 + 0 + 0 = 0
  • 8 ⋅ 0 = 0 ⋅ 8 = 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 = 0
  • 9 ⋅ 0 = 0 ⋅ 9 = 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 = 0
  • 10 ⋅ 0 = 0 ⋅ 10 = 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 = 0

Vynásobte 1

Součin se rovná jinému multiplikátoru jinému než jedné.

  • 1 ⋅ 1 = 1
  • 2 ⋅ 1 = 2 ⋅ 1 = 2
  • 3 ⋅ 1 = 3 ⋅ 1 = 3
  • 4 ⋅ 1 = 4 ⋅ 1 = 4
  • 5 ⋅ 1 = 5 ⋅ 1 = 5
  • 6 ⋅ 1 = 6 ⋅ 1 = 6
  • 7 ⋅ 1 = 7 ⋅ 1 = 7
  • 8 ⋅ 1 = 8 ⋅ 1 = 8
  • 9 ⋅ 1 = 9 ⋅ 1 = 9
  • 10 ⋅ 1 = 10 ⋅ 1 = 10

Vynásobte 2

Přidejte k sobě první faktor.

  • 1 ⋅ 2 = 1 + 1 = 2
  • 2 ⋅ 2 = 2 + 2 = 4
  • 3 ⋅ 2 = 3 + 3 = 6
  • 4 ⋅ 2 = 4 + 4 = 8
  • 5 ⋅ 2 = 5 + 5 = 10
  • 6 ⋅ 2 = 6 + 6 = 12
  • 7 ⋅ 2 = 7 + 7 = 14
  • 8 ⋅ 2 = 8 + 8 = 16
  • 9 ⋅ 2 = 9 + 9 = 18
  • 10 ⋅ 2 = 10 + 10 = 20

Vynásobte 3

První faktor vynásobíme 2 a poté jej přičteme k výsledku.

  • 1 ⋅ 3 = (1 ⋅ 2) + 1 = 2 + 1 = 3
  • 2 ⋅ 3 = (2 ⋅ 2) + 2 = 4 + 2 = 6
  • 3 ⋅ 3 = (3 ⋅ 2) + 3 = 6 + 3 = 9
  • 4 ⋅ 3 = (4 ⋅ 2) + 4 = 8 + 4 = 12
  • 5 ⋅ 3 = (5 ⋅ 2) + 5 = 10 + 5 = 15
  • 6 ⋅ 3 = (6 ⋅ 2) + 6 = 12 + 6 = 18
  • 7 ⋅ 3 = (7 ⋅ 2) + 7 = 14 + 7 = 21
  • 8 ⋅ 3 = (8 ⋅ 2) + 8 = 16 + 8 = 24
  • 9 ⋅ 3 = (9 ⋅ 2) + 9 = 18 + 9 = 27
  • 10 ⋅ 3 = (10 ⋅ 2) + 10 = 20 + 10 = 30

Vynásobte 4

Stejnou částku přidáme ke zdvojnásobenému prvnímu faktoru.

  • 1 ⋅ 4 = (1 ⋅ 2) + (1 ⋅ 2) = 2 + 2 = 4
  • 2 ⋅ 4 = (2 ⋅ 2) + (2 ⋅ 2) = 4 + 4 = 8
  • 3 ⋅ 4 = (3 ⋅ 2) + (3 ⋅ 2) = 6 + 6 = 12
  • 4 ⋅ 4 = (4 ⋅ 2) + (4 ⋅ 2) = 8 + 8 = 16
  • 5 ⋅ 4 = (5 ⋅ 2) + (5 ⋅ 2) = 10 + 10 = 20
  • 6 ⋅ 4 = (6 ⋅ 2) + (6 ⋅ 2) = 12 + 12 = 24
  • 7 ⋅ 4 = (7 ⋅ 2) + (7 ⋅ 2) = 14 + 14 = 28
  • 8 ⋅ 4 = (8 ⋅ 2) + (8 ⋅ 2) = 16 + 16 = 32
  • 9 ⋅ 4 = (9 ⋅ 2) + (9 ⋅ 2) = 18 + 18 = 36
  • 10 ⋅ 4 = (10 ⋅ 2) + (10 ⋅ 2) = 20 + 20 = 40

Vynásobte 5

Pokud je druhý násobitel sudé číslo, výsledek skončí nulou, pokud je lichý, číslem 5.

  • 1 ⋅ 5 = 5 ⋅ 1 = 5
  • 2 ⋅ 5 = 5 ⋅ 2 = 5 + 5 = 10
  • 3 ⋅ 5 = 5 ⋅ 3 = (5 ⋅ 2) + 5 = 15
  • 4 ⋅ 5 = 5 ⋅ 4 = (5 ⋅ 2) + (5 ⋅ 2) = 20
  • 5 ⋅ 5 = 5 + 5 + 5 + 5 + 5 = 25
  • 6 ⋅ 5 = 5 ⋅ 6 = (5 ⋅ 5) + 5 = 30
  • 7 ⋅ 5 = 5 ⋅ 7 = 5 + 5 + 5 + 5 + 5 + 5 + 5 = 35
  • 8 ⋅ 5 = 5 ⋅ 8 = (5 ⋅ 4) + (5 ⋅ 4) = 40
  • 9 ⋅ 5 = 5 ⋅ 9 = (5 ⋅ 10) – 5 = 45
  • 10 ⋅ 5 = 5 ⋅ 10 = 50

Vynásobte 6

První faktor vynásobíme 5, pak k němu přičteme výsledek.

  • 1 ⋅ 6 = (1 ⋅ 5) + 1 = 5 + 1 = 6
  • 2 ⋅ 6 = (2 ⋅ 5) + 2 = 10 + 2 = 12
  • 3 ⋅ 6 = (3 ⋅ 5) + 3 = 15 + 3 = 18
  • 4 ⋅ 6 = (4 ⋅ 5) + 4 = 20 + 4 = 24
  • 5 ⋅ 6 = (5 ⋅ 5) + 5 = 25 + 5 = 30
  • 6 ⋅ 6 = (6 ⋅ 5) + 6 = 30 + 6 = 36
  • 7 ⋅ 6 = (7 ⋅ 5) + 7 = 35 + 7 = 42
  • 8 ⋅ 6 = (8 ⋅ 5) + 8 = 40 + 8 = 48
  • 9 ⋅ 6 = (9 ⋅ 5) + 9 = 45 + 9 = 54
  • 10 ⋅ 6 = (10 ⋅ 5) + 10 = 50 + 10 = 60

Vynásobte 7

Neexistuje žádný zjednodušený algoritmus pro násobení 7, takže používáme metody použitelné pro jiné faktory.

  • 1 ⋅ 7 = 7 ⋅ 1 = 7
  • 2 ⋅ 7 = 7 ⋅ 2 = 7 + 7 = 14
  • 3 ⋅ 7 = 7 ⋅ 3 = (7 ⋅ 2) + 7 = 21
  • 4 ⋅ 7 = 7 ⋅ 4 = (7 ⋅ 2) + (7 ⋅ 2) = 28
  • 5 ⋅ 7 = 7 ⋅ 5 = 7 + 7 + 7 + 7 + 7 = 35
  • 6 ⋅ 7 = 7 ⋅ 6 = (7 ⋅ 5) + 7 = 42
  • 7 ⋅ 7 = 7 + 7 + 7 + 7 + 7 + 7 + 7 = 49
  • 8 ⋅ 7 = 7 ⋅ 8 = (7 ⋅ 4) + (7 ⋅ 4) = 56
  • 9 ⋅ 7 = 7 ⋅ 9 = (7 ⋅ 10) – 7 = 63
  • 10 ⋅ 7 = 70

Vynásobte 8

První faktor vynásobíme 4, stejnou částku pak přidáme k výsledku.

  • 1 ⋅ 8 = (1 ⋅ 4) + (1 ⋅ 4) = 8
  • 2 ⋅ 8 = (2 ⋅ 4) + (2 ⋅ 4) = 16
  • 3 ⋅ 8 = (3 ⋅ 4) + (3 ⋅ 4) = 24
  • 4 ⋅ 8 = (4 ⋅ 4) + (4 ⋅ 4) = 32
  • 5 ⋅ 8 = (5 ⋅ 4) + (5 ⋅ 4) = 40
  • 6 ⋅ 8 = (6 ⋅ 4) + (6 ⋅ 4) = 48
  • 7 ⋅ 8 = (7 ⋅ 4) + (7 ⋅ 4) = 56
  • 8 ⋅ 8 = (8 ⋅ 4) + (8 ⋅ 4) = 64
  • 9 ⋅ 8 = (9 ⋅ 4) + (9 ⋅ 4) = 72
  • 10 ⋅ 8 = (10 ⋅ 4) + (10 ⋅ 4) = 80

Vynásobte 9

První faktor vynásobíme 10 a poté jej odečteme od získaného výsledku.

  • 1 ⋅ 9 = (1 ⋅ 10) – 1 = 10 – 1 = 9
  • 2 ⋅ 9 = (2 ⋅ 10) – 2 = 20 – 2 = 18
  • 3 ⋅ 9 = (3 ⋅ 10) – 3 = 30 – 3 = 27
  • 4 ⋅ 9 = (4 ⋅ 10) – 4 = 40 – 4 = 36
  • 5 ⋅ 9 = (5 ⋅ 10) – 5 = 50 – 5 = 45
  • 6 ⋅ 9 = (6 ⋅ 10) – 6 = 60 – 6 = 54
  • 7 ⋅ 9 = (7 ⋅ 10) – 7 = 70 – 7 = 63
  • 8 ⋅ 9 = (8 ⋅ 10) – 8 = 80 – 8 = 72
  • 9 ⋅ 9 = (9 ⋅ 10) – 9 = 90 – 9 = 81
  • 10 ⋅ 9 = (10 ⋅ 10) – 10 = 100 – 10 = 90

Vynásobte 10

Přidejte nulu na konec druhého násobitele.

  • 1 ⋅ 10 = 10 ⋅ 1 = 10
  • 2 ⋅ 10 = 10 ⋅ 2 = 20
  • 3 ⋅ 10 = 10 ⋅ 3 = 30
  • 4 ⋅ 10 = 10 ⋅ 4 = 40
  • 5 ⋅ 10 = 10 ⋅ 5 = 50
  • 6 ⋅ 10 = 10 ⋅ 6 = 60
  • 7 ⋅ 10 = 10 ⋅ 7 = 70
  • 8 ⋅ 10 = 10 ⋅ 8 = 80
  • 9 ⋅ 10 = 10 ⋅ 9 = 90
  • 10 ⋅ 10 = 10 ⋅ 10 = 100

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