\(\frac{5}{12}-\frac{7}{32}:\frac{21}{16}=\frac{5}{12}-\frac{7}{32}\times\frac{16}{21}=\frac{5}{12}-\frac{112}{672}=\frac{5}{12}-\frac{2}{12}=\frac{3}{12}=\frac{1}{4}\)

\(\frac{5}{12}-\frac{7}{32}:\frac{21}{16}\)

= \(\frac{5}{12}-\frac{1}{6}\)

= \(\frac{1}{4}\)

a, \(\frac{6}{7}.\frac{16}{15}.\frac{7}{6}.\frac{21}{32}=\frac{6}{7}.\frac{7}{6}.\frac{16}{15}.\frac{21}{32}\)=\(1.\frac{16}{15}.\frac{21}{32}=\frac{7}{5.2}=\frac{7}{10}\)

Phần b T²

c,\(\frac{7}{4}.\frac{11}{21}+\frac{11}{21}.\frac{5}{4}=\frac{11}{21}.\left(\frac{7}{4}+\frac{5}{4}\right)\)=\(\frac{11}{21}.3=\frac{11}{7}\)

cảm ơn bạn nha

\(=\dfrac{5}{12}-\dfrac{7}{32}\cdot\dfrac{16}{21}=\dfrac{5}{12}-\dfrac{1}{6}=\dfrac{5}{12}-\dfrac{2}{12}=\dfrac{1}{4}\)

\(\dfrac{5}{12}-\dfrac{7}{32}:\dfrac{21}{16}=\dfrac{5}{12}-\dfrac{7}{32}\times\dfrac{16}{21}=\dfrac{5}{12}-\dfrac{1}{6}=\dfrac{5}{12}-\dfrac{2}{12}=\dfrac{3}{12}=\dfrac{1}{4}\)

a)\(\dfrac{5}{7}+\dfrac{4}{9}=\dfrac{45}{63}+\dfrac{28}{63}=\dfrac{73}{63}\) ; \(\dfrac{9}{11}+\dfrac{3}{8}=\dfrac{72}{88}+\dfrac{33}{88}=\dfrac{105}{88}\)

\(\dfrac{4}{5}-\dfrac{2}{3}=\dfrac{12}{15}-\dfrac{10}{15}=\dfrac{2}{15}\); \(\dfrac{16}{25}-\dfrac{2}{5}=\dfrac{16}{25}-\dfrac{10}{25}=\dfrac{6}{25}\)

b)\(5+\dfrac{3}{5}=\dfrac{25}{5}+\dfrac{3}{5}=\dfrac{28}{5};10-\dfrac{9}{16}=\dfrac{160}{16}-\dfrac{9}{16}=\dfrac{151}{16}\)

\(\dfrac{2}{3}-\left(\dfrac{1}{6}+\dfrac{1}{8}\right)=\dfrac{2}{3}-\left(\dfrac{8}{48}+\dfrac{6}{48}\right)=\dfrac{2}{3}-\dfrac{14}{48}=\dfrac{32}{48}-\dfrac{14}{48}=\dfrac{3}{8}\)

\(\frac{5}{12}-\frac{7}{32}:\frac{21}{16}\)

=\(\frac{5}{12}-\frac{7}{32}.\frac{16}{21}\)

=\(\frac{5}{12}-\frac{1}{6}\)

=\(\frac{5}{12}-\frac{2}{12}\)

=\(\frac{1}{4}\)

125​−327​:1621​=125​−327​×2116​=125​−61​=125​−122​=123​=41​

a)2/5+3/10-1/2=7/10-1/2=2/10=1/5

b)8/11+8/33x3/4=8/11+2/11=10/11

c)7/9x3/14:5/8=1/6:5/8=8/30+4/15

d)5/12-7/32:21/16=5/12-1/6=3/12

nha

a) 2/5+3/10-1/2

= 4/10+3/10-5/10

= 2/10 = 1/5

b) 8/11+8/33x3/4

= 8/11+2/11

= 10/11

c) 7/9x3/14:5/8

= 1/6:5/8

= 1/6x8/5

=4/15

d) 5/12-7/32:21/16

= 5/12-7/32x16/21

= 5/12-1/6

= 5/12-2/12

= 3/12

bạn tự vẽ sơ đồ nhé, con 5 phần ; mẹ 21 phần, mẹ hơn con 32 tuổi

hiệu số phần bằng nhau là :

21 - 5 = 16 ( phần )

tuổi mẹ là :

32 : 16 x 21 = 42 ( tuổi )

tuổi con là :

42 - 32 = 10 ( tuổi )

ĐS : ...
 

Tuổi mẹ là :   32 : ( 21 - 5) x 21 = 42 tuổi 

Tuổi con là : 42 - 32 = 10 tuổi

1/4 có rút gọn rồi nha 

nhưng cậu có thể giải thích là tại sao lại là \(\dfrac{1}{4}\) ko?

5/12 -7/32 :21/16

\(=\frac{5}{12}-\frac{1}{6}\)

\(=\frac{1}{4}\)

5/12 - 7/32 : 21/16 = 5/12 - 112/672

                            = 280/672 - 112/672

                            =   168/672 = 1/4