1+2+3+...+199+200

=(1+200)x200:2

=20100

Học tốt!

1x2x3x4x5x6x7x8x9=362880

100x255+30:100x255-23=26152

a ) 20100

b ) 362880

c ) 25553,5

Đặt tử rồi biểu diễn tử theo mẫu. viết phân số ra rồi dùng tích chéo rồi tìm tử vừa đặt => phân số cần tìm ok

\(\frac{3}{15}\)= \(\frac{3:3}{15:3}\) = \(\frac{1}{5}\)

\(\frac{33}{44}\)= \(\frac{33:11}{44:11}\)= \(\frac{3}{4}\)

\(\frac{2}{8}\)= \(\frac{2:2}{8:2}\)= \(\frac{1}{4}\)

\(\frac{1}{5}\)= \(\frac{1\times4}{5\times4}\)= \(\frac{4}{20}\)

\(\frac{3}{4}\)=\(\frac{3\times5}{4\times5}\)= \(\frac{15}{20}\)

\(\frac{1}{4}\)= \(\frac{1\times5}{4\times5}\)= \(\frac{5}{20}\)

\(\frac{9}{12}\)=\(\frac{9:3}{12:3}\) = \(\frac{3}{4}\)

\(\frac{24}{36}\)=\(\frac{24:12}{36:12}\)= \(\frac{2}{3}\)

\(\frac{3}{8}\)= \(\frac{3:1}{8:1}\)= \(\frac{3}{8}\)

\(\frac{3}{4}\)=\(\frac{3\times6}{4\times6}\)= \(\frac{18}{24}\)

\(\frac{2}{3}\)=\(\frac{2\times8}{3\times8}\)=\(\frac{16}{24}\)

\(\frac{3}{8}\)= \(\frac{3\times3}{8\times3}\)=\(\frac{9}{24}\)

3/15= 1/5; 33/44=3/4; 2/8= 1/4

1/5= 1x 4/ 5x4= 4/20; 3/4= 3x 5/ 4x 5= 15/20; 1/4= 1x 5/ 4x 5= 5/20

9/12= 3/4; 24/36= 2/3; 3/8 không rút gọn được

3/4= 3x 6/ 4x6= 18/24; 2/3= 2x 8/ 3x 8= 16/24; 3/8= 3x 3/ 8x 3= 9/24

a, \(\frac{3}{15}=\frac{1}{5};\frac{33}{44}=\frac{3}{4};\frac{2}{8}=\frac{1}{4}\)

mcs:20

\(\frac{1}{5}=\frac{1x4}{5x4}=\frac{4}{20}:\frac{3}{4}=\frac{3x5}{4x5}=\frac{15}{20};\frac{1}{4}=\frac{1x5}{4x5}=\frac{5}{20}\)

b,\(\frac{9}{12}=\frac{3}{4};\frac{24}{36}=\frac{2}{3};\frac{3}{8}\)

msc:24

\(\frac{3}{4}=\frac{3x6}{4x6}=\frac{18}{24};\frac{2}{3}=\frac{2x8}{3x8}=\frac{16}{24};\frac{3}{8}=\frac{3x3}{8x3}=\frac{9}{34}\)

A

A

A