1 + 2 + 3 +4 + 5 + 19 +18 +17 +16 +15
=[1+19]+[18+2]+[17+3]+[116+4]+[15+5]
=20+20+20+20+20
=100
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Các câu hỏi tương tự
A= 2/1*3 - 4/3*5 + 6/5*7 - ...-16/15*17+ 18/17*19
Tìm 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=?
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+20:15x2
1+2+3+4+5+6+7+8+9+10+11+12+13+14+15+16+17+18+19+20+.........................50= ?
tính nhanh
25/37 x 18/29 + 18/29 x 12/37
31/85 x 11/19 + 31/85 x 12/19 - 42/19 x 31/85
c , 16/53 : 17/9 - 16/53 : 17/8
1/5 x 12/31 x 4/3 + 19/31 x 4/15
a[11+13+15+17+19]-/10+12+14+16+18]
b /9+7+5+3+1]-/8+6+4+2]
1 × 2 + 2 × 3 +3 × 4 + 4 × 5 + 5 × 6 + 6 × 7 + 7 × 8 + 8 × 9 + 9 × 10 + 10 × 11 +11 ×12 + 12 ×13 + 13×14 + 14×15 + 15×16 + 16×17 +17×18 + 18×19 + 19×20 + 20×21 + 21×22 + 22×23 + 23×24 + 24×25 + 25×26