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matematika - zš

hodnota cisla po zväcseni

Prosim Vas, nejako polopatisticky toto vysvetlit? Dakujem.
Pre ktoré číslo platí, že jeho hodnota po zväčšení o 10 percent bude o 6 väčšia ako jeho
hodnota po zmenšení o 10 percent?

1 answer
Peter K.
Peter K. Contact
Vyskúšaj si to najprv na prstoch s hocakým číslo.
Vezmem 20. Zväčším o 10%, to je 20 + (10/100) * 20 = 20 + 2 = 22. Zmenším o 10%, to je 20 - (10/100)*20 = 20 - 2 = 18. Rozdiel je 22 - 18 = 4. Už asi vieš riešeníe, ale teraz ho vypočítame po pansky, lebo to isté, čo sme urobili s 20, urobíme teraz s číslom n.
Pridať 10%: n + (10/100)*n = n + n/10.
Odobrať 10%: n - (10/100)*n = n - n/10.
Rozdiel je (n/10) - (-n/10) = 2*n / 10 = n/5 a má byť 6. Keď pätina n je 6, potom n musí byť päťkrát viac, čiže 30.
Skontroluj si, či to je správne.
Comments:
Anonymous author
Dakujem velmi krasne
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