a) 136 x 68 + 16 x 272 = 136 x 68 + 16 x 2 x 136 = 136 x 68 + 32 x 136 = 136 x ( 68 + 32 ) = 136 x 100 = 13600
b) 8 x 9 x14 + 6 x 17 x 12 + 19 x 4 x18 = 2 x 4 x9 x 14 + 6 x 17 x 4 x 3 + 19 x 4 x 18
= 56 x 18 + 18 x 68 + 76 x 18 = 18 x ( 56 + 68 + 76 ) = 18 x 200 = 3600
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Tính nhanh
a) 23 - 21 + 19 - 17 + 15 - 13 + 11 - 9 + 7 - 5 + 3 - 1;
b) 24 - 22 + 20 - 18 + 16 - 14 + 12 - 10 + 8 - 6 + 4 - 2
1+2+3+4+5+6+7+8+9+10=
11+12+13+14+15+16+17+18+19+20=
1+2+3+4+5+6+7+8+9+10+11+12+13+14 +15+16+17+18+19+20+21+22+23+24+25+26+27+28+29+30-50-53=
bạn5 bạn nào làm nhanh mình sẽ tích cho bạn đó
Tính 21-20+19+18-17-16+15+14-13-12+10+9-8-7+...-5-4+3+2-1
1.Tính tổng sau:
A=1-2+3-4+5-6+7-8+9-10+11-12+13-14+15-16+17-18+19-20.
1+2+3+4+5+6+7+8+9+10=
11+12+13+14+15+16+17+18+19+20=
1+2+3+4+5+6+7+8+9+10+11+12+13+14 +15+16+17+18+19+20+21+22+23+24+25+26+27+28+29+30-50-53=bạn5 bạn nào làm nhanh mình sẽ tích cho bạn đó
M = { 1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9 + 10 + 11 + 11 + 12 + 13 + 14 + 15 + 16 + 17 + 18+ 19 + 20 }
Bài 6 : Tính .
a , A = - 1 + 3 - 5 + 7 - 9 + 11 - 13 + 15 - 17
b , B = 1 + 2 - 3 - 4 + 5 + 6 - 7 - 8 + 9 + 10 - 11 -12 + 13 + 14 - 15 -16 + 17 + 18 - 19 - 20
1-2-3-4-5-6-7-8-9-10-11-12-13-14-15-16-17-18-19-20
