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S
1 tháng 3 2017
a) Cách 1 : (3/4 + 1/2) x 5/7
= 5/4 x 5/7
= 25/28
Cách 2 : (3/4 + 1/2) x 5/7
= 3/4 x 5/7 + 1/2 x 5/7
= 15/28 + 5/14
= 25/28
b) Cách 1 : 5/7 x 13/21 + 2/7 x 13/21
= 65/147 + 26/147
= 13/21
Cách 2 : 5/7 x 13/21 + 2/7 x 13/21
= (5/7 + 2/7) x 13/21
= 1 x 13/21
= 13/21
câu c tự làm
LT
1
3 tháng 3 2022
a: \(=\dfrac{3\cdot2+5}{10}\cdot\dfrac{4}{5}=\dfrac{11}{10}\cdot\dfrac{4}{5}=\dfrac{44}{50}=\dfrac{22}{25}\)
b: \(=\dfrac{2}{5}\left(\dfrac{3}{7}+\dfrac{4}{7}\right)=\dfrac{2}{5}\)
SC
1
HT
2
S
2 tháng 3 2023
cách 1 \(\left(\dfrac{6}{11}+\dfrac{7}{5}\right)\cdot\dfrac{3}{7}\\ =\dfrac{107}{55}\cdot\dfrac{3}{7}=\dfrac{321}{385}\)cách 2 \(\left(\dfrac{6}{11}+\dfrac{7}{5}\right)\cdot\dfrac{3}{7}\\ =\dfrac{6}{11}\cdot\dfrac{3}{7}+\dfrac{7}{5}\cdot\dfrac{3}{7}\\ =\dfrac{18}{77}+\dfrac{3}{5}=\dfrac{321}{385}\)
cách 1 \(\left(\dfrac{6}{7}-\dfrac{1}{2}\right)\cdot\dfrac{2}{5}\\ =\dfrac{5}{14}\cdot\dfrac{2}{5}=\dfrac{1}{7}\) cách 2 \(\left(\dfrac{6}{7}-\dfrac{1}{2}\right)\cdot\dfrac{2}{5}\\ =\dfrac{6}{7}\cdot\dfrac{2}{5}-\dfrac{1}{2}\cdot\dfrac{2}{5}\\ =\dfrac{12}{35}-\dfrac{1}{5}=\dfrac{1}{7}\)
NT
Nguyễn Thị Thương Hoài
Giáo viên
VIP
2 tháng 3 2023
[ \(\dfrac{6}{11}\) + \(\dfrac{7}{5}\)] x \(\dfrac{3}{7}\)
= [ \(\dfrac{30}{55}\) + \(\dfrac{77}{55}\)] x \(\dfrac{3}{7}\)
= \(\dfrac{107}{55}\)x \(\dfrac{3}{7}\)
= \(\dfrac{321}{385}\)
[ \(\dfrac{6}{11}\) + \(\dfrac{7}{5}\)] x \(\dfrac{3}{7}\)
= \(\dfrac{6}{11}\) x \(\dfrac{3}{7}\) + \(\dfrac{7}{5}\) x \(\dfrac{3}{7}\)
= \(\dfrac{18}{77}\) + \(\dfrac{3}{5}\)
= \(\dfrac{90}{385}\) + \(\dfrac{231}{385}\)
= \(\dfrac{321}{385}\)
[ \(\dfrac{6}{7}\) - \(\dfrac{1}{2}\)] x \(\dfrac{2}{5}\)
= [ \(\dfrac{12}{14}\) - \(\dfrac{7}{14}\)] x \(\dfrac{2}{5}\)
= \(\dfrac{5}{14}\) x \(\dfrac{2}{5}\)
= \(\dfrac{1}{7}\)
[ \(\dfrac{6}{7}\) - \(\dfrac{1}{2}\)] x \(\dfrac{2}{5}\)
= \(\dfrac{6}{7}\) x \(\dfrac{2}{5}\) - \(\dfrac{1}{2}\) x \(\dfrac{2}{5}\)
= \(\dfrac{12}{35}\) - \(\dfrac{1}{5}\)
= \(\dfrac{12}{35}\) - \(\dfrac{7}{35}\)
= \(\dfrac{5}{35}\)
= \(\dfrac{1}{7}\)
TN
1
S
4
TB
4
NK
19 tháng 3 2023
\(a,\left(\dfrac{1}{3}+\dfrac{1}{5}\right)\times\dfrac{1}{4}=\dfrac{8}{15}\times\dfrac{1}{4}=\dfrac{8}{60}=\dfrac{2}{15}\)
\(\left(\dfrac{1}{3}+\dfrac{1}{5}\right)\times\dfrac{1}{4}=\dfrac{1}{3}\times\dfrac{1}{4}+\dfrac{1}{5}\times\dfrac{1}{4}=\dfrac{1}{12}+\dfrac{1}{20}=\dfrac{20}{240}+\dfrac{12}{240}=\dfrac{32}{240}=\dfrac{2}{15}\)
\(b,\dfrac{2}{5}\times\dfrac{3}{7}+\dfrac{2}{5}\times\dfrac{4}{7}=\dfrac{2}{5}\times\left(\dfrac{3}{7}+\dfrac{4}{7}\right)=\dfrac{2}{5}\times1=\dfrac{2}{5}\)
\(\dfrac{2}{5}\times\dfrac{3}{7}+\dfrac{2}{5}\times\dfrac{4}{7}=\dfrac{6}{35}+\dfrac{8}{35}=\dfrac{14}{35}=\dfrac{2}{5}\)
19 tháng 3 2023
trả lời nhanh nha! trả lời trong tối hôm nay 19/3/2023 ạ
5 x 2 x 7 =?
Cách 1:
5 x 2 x 7 = (5 x 2) x 7 = 10 x 7 = 70
2: 5 x 2 x 7 = 5 x ( 2 x 7) = 5 x 14 = 70