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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) \(\left(\frac{2}{7}+\frac{3}{8}+\frac{12}{7}+\frac{5}{8}\right).\frac{19}{36}\)
\(=\left\{\left(\frac{2}{7}+\frac{12}{7}\right)+\left(\frac{3}{8}+\frac{5}{8}\right)\right\}.\frac{19}{36}\)
\(=\left(\frac{14}{7}+\frac{8}{8}\right).\frac{19}{36}\)
\(=\left(2+1\right).\frac{19}{36}\)
\(3.\frac{19}{36}=\frac{19}{12}\)
mỗi một dòng cuối câu vẫn phải viết thêm `
vd:
`3xx4/15-2xx4/15-5xx4/15`
`=4/15xx(3-2-5)`
`=4/15xx-4`
`=-16/15`
\(\left(\dfrac{2}{7}+\dfrac{5}{7}\right)+\left(\dfrac{3}{5}+\dfrac{2}{5}\right)+\left(\dfrac{3}{8}+\dfrac{4}{8}+\dfrac{1}{8}\right)+\left(\dfrac{1}{9}+\dfrac{8}{9}\right)=1+1+1+1=4\)
13/8:5/6:3/5-2/3
=13/8x6/5x5/3-2/3
=13/8x[6/5x5/3]-2/3
=13/8x2-2/3
=13/4-2/3
=39/12-8/12
=31/12
\(\dfrac{3}{12}\)x\(\dfrac{15}{6}\)x\(\dfrac{8}{5}\)
=> \(\dfrac{5}{8}\)x\(\dfrac{8}{5}\)
=>1
Bài làm
\(\frac{7}{15}x\frac{3}{8}+\frac{7}{15}x\frac{5}{8}\)
= \(\frac{7}{15}x\left(\frac{3}{8}+\frac{5}{8}\right)\)
= \(\frac{7}{15}x\frac{8}{8}\)
= \(\frac{7}{15}x1\)
= \(\frac{7}{15}\)
# Chúc bạn học tốt #
\(\frac{7}{15}\cdot\frac{3}{8}+\frac{7}{15}\cdot\frac{5}{8}\)
\(=\frac{7}{15}\cdot(\frac{3}{8}+\frac{5}{8})\)
\(=\frac{7}{15}\cdot1=\frac{7}{15}\)
`2/3 xx 2/8 +2/3 : 8 +2/3 xx 5/8`
`=2/3 xx 2/8 +2/3 xx 1/8 +2/3 xx 5/8`
`=2/3 xx (2/8+1/8+5/8)`
`=2/3 xx 8/8`
`=2/3 xx 1`
`=2/3`
8/15+2/3=18/15=6/5 3/8+4/8=7/8 tính thuận tiện: 3/2+2/3+4/3=3/2+(2/3+4/3)=3/2+2=7/2 3/5+7/5+3/4=(3/5+7/5)+3/4=2+3/4=11/4 hình như cái đầu tiên chép sai đề????????????????
2/15 x 3/8 + 3/8 x 2/3 + 3/8 : 5
= 2/15 x 3/8 + 3/8 x 2/3 + 3/8 x 1/5
= 3/8 x ( 2/15 + 2/3 + 1/5 )
= 3/8 x 1
= 3/8
~ Hok tốt ~
#Minh#
\(\frac{2}{15}\cdot\frac{3}{8}+\frac{3}{8}\cdot\frac{2}{3}+\frac{3}{8}:5\)
\(=\frac{3}{8}\cdot\left(\frac{2}{15}+\frac{2}{3}+1\right):5\)
\(=\frac{3}{8}\cdot\frac{9}{5}:5=\frac{27}{100}\)