Câu 8
3/5 : x = 3
x = 3/5 : 3
x = 1/5
Câu 9
a) 1/5 + 4/11 + 4/5 + 7/11
= ( 1/5 + 4/5 ) + ( 4/11 + 7/11 )
= 1 + 1
= 2
b) 5/6 + ( 5/9 - 1/4 )
= 5/6 + 7/18
= 11/9
Mình sửa lại câu 9 b
b) 5/6 + ( 5/9 - 1/4 )
= 5/6 + ( 20/36 - 9/36 )
= 5/6 + 11/36
= 30/36 + 11/36
= 41/36
Câu 8 : Tìm x
\(\dfrac{3}{5}\) : x = 3
x = \(\dfrac{3}{5}\) : 3 = \(\dfrac{3}{5}\) : \(\dfrac{3}{1}\) = \(\dfrac{3}{5}\) x \(\dfrac{1}{3}\)
x = \(\dfrac{3}{15}\) = \(\dfrac{1}{5}\)
Câu 9 :
a) \(\dfrac{1}{5}\) + \(\dfrac{4}{11}\) + \(\dfrac{4}{5}\) + \(\dfrac{7}{11}\)
= ( \(\dfrac{1}{5}\) + \(\dfrac{4}{5}\) ) + ( \(\dfrac{4}{11}\) + \(\dfrac{7}{11}\) )
= 1 + 1
= 2
b) \(\dfrac{5}{6}\) + ( \(\dfrac{5}{9}\) - \(\dfrac{1}{4}\) )
= \(\dfrac{5}{6}\) + ( \(\dfrac{20}{36}\) - \(\dfrac{9}{36}\) )
= \(\dfrac{5}{6}\) + \(\dfrac{11}{36}\)
= \(\dfrac{30}{36}\) + \(\dfrac{11}{36}\)
= \(\dfrac{41}{36}\)
