Efectuează,utilizând factorul comun
Răspunsuri la întrebare
a) 110 + 220 + 330 + 440 + 550 = 1650
= 110 × ( 1 + 2 + 3 + 4 + 5 ) =
= 110 × 15 =
= 1 650
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c))
5 + 10 + 15 + 20 + 25 + 30 = 105
= 5 × ( 1 + 2 + 3 + 4 + 5 + 6 ) =
= 5 × 21 =
= 105
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b) 11 001 + 22 002 + 33 003 + 44 004 + 55 005 = 165 015
= 11 001 × ( 1 + 2 + 3 + 4 + 5 ) =
= 11 001 × 15 =
= 165 015
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d)
6 + 12 + 18 + 24 + 30 + 36 + 42 = 168
= 6 × ( 1 + 2 + 3 + 4 + 5 + 6 + 7 ) =
= 6 × 28 =
= 168
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e) 123 × 389 + 123 × 11 - 100 × 123 = 36 900
= 123 × ( 389 + 11 - 100 ) =
= 123 × ( 400 - 100 ) =
= 123 × 300 =
= 36 900
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f)
719 × 2 017 - 2 017 + 282 × 2017 = 2 017 000
= 2 017 × ( 719 - 1 + 282 ) =
= 2 017 × ( 718 + 282 ) =
= 2 017 × 1 000 =
= 2 017 000
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g) 739 × 2 016 - 2 016 + 262 × 2016 = 2 016 000
= 2 016 × ( 739 - 1 + 262 ) =
= 2 016 × ( 738 + 262 ) =
= 2 016 × 1 000 =
= 2 016 000
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h) 1 999 × 2 000 - 1 998 × 1 999 - 2 × 1 998 = 2
= 1 999 × ( 2 000 - 1 998 ) - 2 × 1 998
= 1 999 × 2 - 2 × 1 998 =
= 2 × ( 1 999 - 1 998 ) =
= 2