Question

Dați factor comun apoi calculați a) 10 +20 + 30 .... + 800 b) 13 + 26 +39 + ......+ 715 c) 21+ 42 +36 +...+ 1890 d) 101 + 202 + 303+......+ 909 +
1010 +...+ 9898 +9999



URGENT DAU COROANA ​

Answer 1

Răspuns:

a ) 10 ( 1+ 2 + 3 + ..... + 80 )

10 * (80 * 45) = 36000

b ) 13 ( 1 + 2 + 3 .... + 55 )

13 * ( 55 * 56 ) / 2

13 * 55 * 28 = 20020

c ) 21 ( 1 + 2 + 3 +... + 90 )

21 * 90 * 91 / 2 = 85995

d ) 101 ( 1 + 2 + 3 +...+ 99 )

101 * 99 * 100 / 2 = 499950