Lời giải:
$\frac{18}{35}\times \frac{5}{16}-\frac{5}{16}\times \frac{2}{7}$
$=\frac{5}{16}\times (\frac{18}{35}-\frac{2}{7})$
$=\frac{5}{16}\times \frac{8}{35}=\frac{1}{14}$
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+31+32+33+34+35+36+37=
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+31+32+33+34+35+36+37+38+39+40+41+42+43+44+45+46+47+48+49+50=?
11+2+3+4+5+6+7+8+9+10+11+12+13+14+15+16+17+18+19+20=?
mik tích cho 5 người trả lời nhanh nhất trong ngày hôm nay
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=
[TEX]\frac{x}{2} = \frac{y}{3} <=> \frac{x}{8} = \frac{y}{12}[/TEX]
[TEX]\frac{y}{4} = \frac{z}{5} <=> \frac{y}{12} = \frac{z}{15}[/TEX]
Suy ra:
[TEX]\frac{x}{8} = \frac{y}{12} = \frac{z}{15} [/TEX]
Mặt khác: [TEX]x+y+z=10 [/TEX]
Áp dụng tính chấmơẻ rộng của dãy tỉ số bằng nhau:
[TEX]\frac{x+y+z}{8+12+15} = \frac{10}{35} = \frac{2}{7} [/TEX]
[TEX]x= \frac{16}{7}[/TEX]
[TEX]y= \frac{24}{7}[/TEX]
[TEX]z= \frac{30}{7}[/TEX]
1+2+3+4+5+6+7+8+9+10+11+12+13+14+15+16+17+18+19+20=bao nhiêu?
Tính:1-2+3-4+5-6+7-8+9-10+11-12+13-14+15-16+17-18+19-20+21
1+1+2+3+4+5+6+7+8+9+10+11+12+13+14+15+16+17+18+19+20=may
