uk 

cj mới sang hoidap hay lâu r 

Cuộn dây điện dài là:

70:\(\dfrac{7}{10}\)=100(m)

S

Đ

S

Đ

lm thiếu

1)

=\(\dfrac{2}{4}\)+\(\dfrac{1}{4}\)

=\(\dfrac{3}{4}\)

2)

=\(\dfrac{24}{26}\)-\(\dfrac{21}{26}\)

=\(\dfrac{3}{26}\)

3)

=\(\dfrac{7}{4}\)-\(\dfrac{7}{19}\)

=\(\dfrac{133}{76}\)-\(\dfrac{28}{76}\)

=\(\dfrac{105}{76}\)

4)

=\(\dfrac{11}{6}\)-\(\dfrac{9}{13}\)

=\(\dfrac{143}{78}\)-\(\dfrac{54}{78}\)

=\(\dfrac{89}{78}\)

Nguyễn Văn Ngọc san

hi cj min