Đáp án:
Đề mik ko chép lại nha
Giải thích các bước giải:
a) Cách 1:
$\frac{1}{12}$ + $\frac{2}{24}$
= $\frac{1}{12}$ + $\frac{1}{12}$
= $\frac{2}{12}$
= $\frac{1}{6}$
Cách 2:
$\frac{1}{12}$ + $\frac{2}{24}$
= $\frac{2}{24}$ + $\frac{2}{24}$
= $\frac{4}{24}$
= $\frac{1}{6}$
b)
= $\frac{15}{40}$ + $\frac{5}{40}$
= $\frac{20}{40}$
= $\frac{1}{2}$
c)
= $\frac{5}{56}$ - $\frac{3}{8}$
= $\frac{5}{56}$ - $\frac{21}{56}$
= $\frac{- 16}{56}$
= $\frac{-2}{7}$
d)
= $\frac{90}{27}$ + $\frac{5}{27}$
= $\frac{95}{27}$
e)
= $\frac{5}{42}$ + $\frac{35}{42}$
= $\frac{40}{42}$
= $\frac{20}{21}$
f)
( giống câu b)
g)
= $\frac{30}{36}$ + $\frac{4}{36}$
= $\frac{34}{36}$
= $\frac{17}{18}$
h)
= $\frac{21}{49}$ - $\frac{2}{49}$
= $\frac{19}{49}$
i)
= $\frac{49}{63}$ + $\frac{5}{63}$
= $\frac{54}{63}$
= $\frac{6}{7}$
j)
= $\frac{15}{54}$ + $\frac{20}{54}$
= $\frac{35}{54}$
