Question

[Nguyễn Thị Phương Thảo]

tính hợp lý giá trị các biểu thức sau :

B= 71\(\dfrac{38}{45}\) - ( 43\(\dfrac{8}{45}\) - 1\(\dfrac{17}{57}\) )

D= ( 19\(\dfrac{5}{8}\) : \(\dfrac{7}{12}\) - 13\(\dfrac{1}{4}\) : \(\dfrac{7}{12}\) ) . \(\dfrac{4}{5}\)

F= ( 9,75 . 21\(\dfrac{3}{7}\) + \(\dfrac{39}{4}\) . 18\(\dfrac{4}{7}\) ). \(\dfrac{15}{78}\)

Answer 1

[Nguyễn Hồng Ánh]

F=(9.75.21\(\dfrac{3}{7}\)+\(\dfrac{39}{4}\).18\(\dfrac{4}{7}\)).\(\dfrac{15}{78}\)

=(\(\dfrac{39}{4}\).21\(\dfrac{3}{7}\)+\(\dfrac{39}{4}\).18\(\dfrac{4}{7}\)).\(\dfrac{15}{78}\)

=[\(\dfrac{39}{4}\).(21\(\dfrac{3}{7}\)+18\(\dfrac{4}{7}\))].\(\dfrac{15}{78}\)

=[\(\dfrac{39}{4}\).(21+18)+(\(\dfrac{3}{7}\)+\(\dfrac{4}{7}\))].\(\dfrac{15}{78}\)

=[\(\dfrac{39}{4}\).(39+1)].\(\dfrac{15}{78}\)

=(\(\dfrac{39}{4}\).40).\(\dfrac{15}{78}\)

=390.\(\dfrac{15}{78}\)=75

Answer 2

[Đức Hiếu]

\(B=71\dfrac{38}{45}-\left(43\dfrac{8}{45}-1\dfrac{17}{57}\right)\)

\(B=71\dfrac{38}{45}-43\dfrac{8}{45}-1\dfrac{17}{57}\)

\(B=28\dfrac{2}{3}-1\dfrac{17}{57}=27\dfrac{11}{57}\)

\(D=\left(19\dfrac{5}{8}:\dfrac{7}{12}-13\dfrac{1}{4}:\dfrac{7}{12}\right).\dfrac{4}{5}\)

\(D=\dfrac{12}{7}.\left(19\dfrac{5}{8}-13\dfrac{1}{4}\right).\dfrac{4}{5}\)

\(D=\dfrac{12}{7}.\dfrac{51}{8}.\dfrac{4}{5}=\dfrac{306}{35}\)

Câu còn lại làm tương tự!

Chúc bạn học tốt!!!