Răspuns :

Alin501id

10+20+30+...+700=10×(1+2+3+...+70)=

=10×70×71:2=10×35×71=24850

1DianaMaria3id

[tex]10 + 20 + 30 + ... + 700 = \\ = 10(1 + 2 + 3 + ... + 70) = \\ = 10 \times \frac{70 \times 71}{2} = \\ = 10 \times \frac{4970}{2} = \\ = 10 \times 2485 = \\ = 24850[/tex]

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