Question

Gasiti si scoateti un factor comun, cand calculati urmatoarele sume:
f) 25+50+75+100+...+400;
g)10+20+30+40+...+480;
h)6+12+18+24+...+1200.
DAU COROANA LA CINE SCRIE PRIMUL TOATE!!!!!!

Answer 1

Răspuns:

Explicație pas cu pas:

f)

25 + 50 + 75 + 100 + ..... + 400 =

= 25 × ( 1 + 2 + 3 + 4 + ...... + 16 ) =

= 25 × [ 16 × ( 1 + 16 ) : 2 ] =

= 25 × ( 8 × 17 ) =

= 25 × 136 =

= 3 400

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g)

10 + 20 + 30 + 40 + ...... + 480 =

= 10 × ( 1 + 2 + 3 + 4 + ..... + 40 ) =

= 10 × [ 40 × ( 1 + 40 ) : 2 ] =

= 10 × ( 20 × 41 ) =

= 10 × 820 =

= 8 200

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h)

6 + 12 + 18 + 24 + ...... + 1 200 =

= 6 × ( 1 + 2 + 3 + 4 + ...... + 200 ) =

= 6 × [ 200 × ( 1 + 200 ) : 2 ] =

= 6 × ( 100 × 201 ) =

= 6 × 20 100 =

= 120 600