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a . 4040 cm2 = 40 dm2 40 cm2
b . 2 000 324 m2 = 2 km2 324 m2
c . 7 km2 27 m2 = 7 000 027 m2
d . 300 000 000 cm2 = 30 000 m2
a) A = \(\frac{1}{11}+\frac{1}{12}+\frac{1}{13}+...+\frac{1}{30}\)
A > \(\frac{1}{30}+\frac{1}{30}+\frac{1}{30}+...+\frac{1}{30}\)
A > \(\frac{1}{30}.20\)
A > \(\frac{2}{3}\)
Vậy A > \(\frac{2}{3}\)
b) A = \(\frac{1}{11}+\frac{1}{12}+\frac{1}{13}+...+\frac{1}{30}\)
A < \(\frac{1}{11}+\frac{1}{11}+\frac{1}{11}+...+\frac{1}{11}\)
A < \(\frac{1}{11}.20\)
A < \(\frac{20}{11}\)
Mà \(\frac{20}{11}\)\(< 2\)
=> A < 2
Vậy A <2
ỦNG HỘ NHA
a) \(\frac{1}{2}+\frac{1}{4}< \frac{3}{4}+\frac{1}{5}\)
b) \(\frac{7}{13}+\frac{2}{9}>\frac{3}{26}+\frac{7}{13}\)
~ GHÉT ..............................~
a) \(\frac{1}{2}+\frac{1}{4}< \frac{3}{4}+\frac{1}{5}\)
b) \(\frac{7}{13}+\frac{2}{9}>\frac{3}{26}+\frac{7}{13}\)
Bài 1:
a) \(\frac{3}{4}×\frac{4}{7}=\frac{3×4}{4×7}=\frac{3}{7}\)
\(\frac{12}{35}:\frac{3}{5}=\frac{12}{35}×\frac{5}{3}=\frac{12×5}{35×3}=\frac{4.}{7}\)
\(\frac{4}{7}×\frac{3}{5}=\frac{4×3}{7×5}=\frac{12}{35}\)
b) \(\frac{13}{11}×2=\frac{13×2}{11}=\frac{26}{11}\)
\(\frac{26}{11}:\frac{13}{11}=\frac{26}{11}×\frac{11}{13}=\frac{26×11}{11×13}=\frac{2×1}{1×1}=\frac{2}{1}=2\)
\(\frac{26}{11}:2=\frac{26}{11}×\frac{1}{2}=\frac{26×1}{11×2}=\frac{13×1}{11×1}=\frac{13}{11}\)
\(2×\frac{13}{11}=\frac{2×13}{11}=\frac{26}{11}\)
k giúp mik ✅
Bài 2:
a) \(\frac{4}{7}×\:x\:=\frac{1}{3}\)
\(\Rightarrow\)x = \(\frac{1}{3}-\frac{4}{7}\)
\(\Rightarrow\)x = \(\frac{7}{21}-\frac{4}{21}\)
\(\Rightarrow\)x = \(\frac{3}{21}=\frac{1}{7}\)
b) x : \(\frac{2}{5}=\frac{2}{9}\)
\(\Rightarrow\)x = \(\frac{2}{9}×\frac{2}{5}\)
\(\Rightarrow\)x = \(\frac{4}{45}\)
a, 138 c m 2 < 13 d m 2 8 c m 2
Ta có: 13 d m 2 8 c m 2 = 1300 c m 2 + 8 c m 2 = 1308 c m 2 > 138 c m 2
hay 138 c m 2 < 1308 c m 2
b, 300 d m 2 > 2 m 2 99 d m 2
Ta có 2 m 2 99 d m 2 = 200 d m 2 + 99 d m 2 = 299 d m 2 < 300 d m 2
Hay 300 d m 2 > 299 d m 2