Ajutați ma va rog cu ex 14 și 15 de pe fisa
Răspunsuri la întrebare
14)
a) 235 × 675 + 793 × 675 + 325 × 1 028 = 1 028 000
= 675 × ( 235 + 793 ) + 325 × 1 028 =
= 675 × 1 028 + 325 × 1 028 =
= 1 028 × ( 675 + 325 ) =
= 1 028 × 1 000 =
= 1 028 000
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b) 309 × 576 + 576 × 894 + 424 × 1 203 = 1 203 000
= 576 × ( 309 + 894 ) - 424 × 1 203 =
= 576 × 1 203 + 424 × 1 203 =
= 1 203 × ( 576 + 424 ) =
= 1 203 × 1 000 =
= 1 203 000
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c) 729 × 473 - 473 × 275 + 454 × 1 027 = 681 000
= 473 × ( 729 - 275 ) + 454 × 1 027 =
= 473 × 454 + 454 × 1 027 =
= 454 × ( 473 + 1 027 ) =
= 454 × 1 500 =
= 681 000
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d) 506 × 825 + 918 × 506 - 1 743 × 306 = 348 600
= 506 × ( 825 + 918 ) - 1 743 × 306
= 506 × 1 743 - 1 743 × 306 =
= 1 743 × ( 506 - 306 ) =
= 1 743 × 200 =
= 348 600
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15)
S₁ = 2 + 4 + 6 + ........ + 1 000
S₁ = 2 × ( 1 + 2 + 3 + ...... + 500 )
S₁ = 2 × 500 × ( 1 + 500 ) : 2
S₁ = 500 × 501
S₁ = 250 500
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S₂ = 3 + 6 + 9 + ........ + 2013
S₂ = 3 × ( 1 + 2 + 3 + ...... + 671 )
S₂ = 3 × 671 × ( 1 + 671 ) : 2
S₂ = 2 013 × 678 : 2
S₂ = 2013 × 339
S₂ = 682 407
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S₃ = 5 + 10 + 15 + .......+ 500
S₃ = 5 × ( 1 + 2 + 3 + ...... + 100 )
S₃ = 5 × 100 × 101 : 2
S₃ = 505 × 50
S₃ = 25 250
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S₄ = 7 + 14 + 21 + .......... + 700
S₄ = 7 × ( 1 + 2 + 3 + ..... + 100 )
S₄ = 7 × 100 × 101 : 2
S₄ = 707 × 50
S₄ = 35 350