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A = (2 + 22) + (23 + 24 ) +…(2199 + 2200)
A = 6 + 22 (2 + 22 ) +… + 2198 (2 + 22)
A = 6 + 22 (6 ) +… + 2198 (6)
A = 6(1 + 22 +… + 2198)
Vậy A chia hết cho 6
a) \(\left(\frac{2}{7}+\frac{3}{8}+\frac{12}{7}+\frac{5}{8}\right).\frac{19}{36}\)
\(=\left\{\left(\frac{2}{7}+\frac{12}{7}\right)+\left(\frac{3}{8}+\frac{5}{8}\right)\right\}.\frac{19}{36}\)
\(=\left(\frac{14}{7}+\frac{8}{8}\right).\frac{19}{36}\)
\(=\left(2+1\right).\frac{19}{36}\)
\(3.\frac{19}{36}=\frac{19}{12}\)
\(\frac{1}{8}+\frac{1}{12}+\frac{3}{8}+\frac{5}{12}\)
\(=\left(\frac{1}{8}+\frac{3}{8}\right)+\left(\frac{1}{12}+\frac{5}{12}\right)\)
\(=\frac{4}{8}+\frac{6}{12}\)
\(=\frac{1}{2}+\frac{1}{2}=\frac{1+1}{2}=\frac{2}{2}=1\)
1/8 + 1/12 + 3/8 + 5/12
= ( 1/8 + 3/8 ) + ( 1/12 + 5/12 )
= 4/8 + 6/12
= 1/2 + 1/2
= 2/2
= 1
Chúc học giỏi !!!
1) \(\frac{1}{12}+\frac{1}{16}+\frac{3}{4}\)
\(=\frac{4}{48}+\frac{3}{48}+\frac{36}{48}\)
\(=\frac{4+3+36}{48}\)
\(=\frac{43}{48}\)
2) a) \(\frac{1}{15}+\frac{4}{15}+\frac{5}{18}+\frac{7}{18}\)
\(=\left(\frac{1}{15}+\frac{4}{15}\right)+\left(\frac{5}{18}+\frac{7}{18}\right)\)
\(=\frac{1}{3}+\frac{2}{3}=1\)
b) \(\frac{1}{8}+\frac{1}{12}+\frac{3}{8}+\frac{5}{12}\)
\(=\left(\frac{1}{8}+\frac{3}{8}\right)+\left(\frac{1}{12}+\frac{5}{12}\right)\)
\(=\frac{1}{2}+\frac{1}{2}=1\)
\(\frac{1}{2}+\frac{2}{4}+\frac{3}{6}+\frac{4}{8}+\frac{5}{10}+\frac{6}{12}\)
\(=\frac{1}{2}+\frac{1}{2}+\frac{1}{2}+\frac{1}{2}+\frac{1}{2}+\frac{1}{2}\)
\(=6\times\frac{1}{2}=3\)
Tính bằng cách thuận tiện nhất
Giải
a ) \(\left(\frac{3}{5}+\frac{2}{5}\right)+\left(\frac{4}{7}+\frac{3}{7}\right)\) b) \(\left(\frac{1}{8}+\frac{7}{8}\right)+\left(\frac{1}{12}+\frac{5}{12}\right)\)
=> \(1\) \(+\) \(1\) => \(1\) \(+\) \(\frac{1}{6}\)
=> \(2\) => \(\frac{7}{6}\)
Theo mk là vậy. Nếu đúng thì tk nha!
\(\frac{3}{5}+\frac{4}{7}+\frac{2}{5}+\frac{3}{7}\)
\(=\left(\frac{3}{5}+\frac{2}{5}\right)+\left(\frac{4}{7}+\frac{3}{7}\right)\)
\(=\frac{5}{5}+\frac{7}{7}\)
\(=1+1=2\)
\(a.60\times\left(\frac{7}{12}+\frac{4}{15}\right)\)
\(=60\times\left(\frac{35}{60}+\frac{16}{60}\right)\)
\(=60\times\frac{51}{60}\)
\(=51\)
\(b.\frac{1}{2}\times\frac{2}{3}\times\frac{3}{4}\times\frac{4}{5}\times\frac{5}{6}\times\frac{6}{7}\times\frac{7}{8}\times\frac{8}{9}\)
\(=\frac{1\times2\times3\times4\times5\times6\times7\times8}{2\times3\times4\times5\times6\times7\times8\times9}\)
\(=\frac{1}{9}\)
1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9 + 10 + 11 + 12
= ( 1 + 12 ) + ( 2 + 11 ) + ( 3 + 10 ) + ( 4 + 9 ) + ( 5 + 8 ) + ( 6 + 7 )
= 13 + 13 + 13 + 13 + 13 + 13
= 13 x 6
= 78
sai thui
Tính bằng cách thuận tiện nhất
a,5*12*3*7/3*8*7*5
b, 2*5*4*6/4*3*5*7
Làm nhanh nha , mình đang cần gấp
a)
\(\frac{5.12.3.7}{3.8.7.5}=\frac{1.12.1.1}{1.8.1.10}=\frac{12}{8}=\frac{3}{2}\)
b)
\(\frac{2.5.4.6}{4.3.5.7}\frac{2.1.1.2.3}{1.1.1.7}=\frac{12}{7}\)
HOK TỐT!
\(\frac{8.9.15}{12.6.15}=\frac{8.9}{12.6}=1\)
\(\frac{7.3.5}{8.7.3}=\frac{5}{8}--\)gạch héo các ht giống nhau trên vá dưới mẫu các ý kia tương tự
\(\frac{2.9.4}{12.9.2}=\frac{4}{12}=\frac{1}{3}\)
\(\frac{1515}{2525}=\frac{1515:505}{2525:505}=\frac{3}{5}\)
LÀM CÁCH LÀM ĐẦY ĐỦ NHA MÌNH KHÔNG HIỂU NHA
\(\dfrac{7}{12}\) + \(\dfrac{2}{3}\) + \(\dfrac{3}{8}\) + \(\dfrac{5}{12}\) + \(\dfrac{1}{3}\) + \(\dfrac{5}{8}\)
= (\(\dfrac{7}{12}\) + \(\dfrac{5}{12}\)) + (\(\dfrac{2}{3}\) + \(\dfrac{1}{3}\)) + (\(\dfrac{3}{8}\) + \(\dfrac{5}{8}\))
= 1 + 1 + 1
= 2 + 1
= 3
=(\(\dfrac{7}{12}\)+\(\dfrac{5}{12}\))+(\(\dfrac{2}{3}\)+\(\dfrac{1}{3}\))+(\(\dfrac{3}{8}\)+\(\dfrac{5}{8}\))
=1+1+1
=3