`3/4 xx  8/9 xx 15/16 xx 24/25 xx 35/36`

`= (3xx8xx15xx24xx35)/(4xx9xx16xx25xx36)`

`=(3xx4xx2xx5xx3xx4xx6xx7xx5)/(4xx3xx3xx4xx4xx5xx5xx6xx6)`

`=(2xx7)/(4xx6)`

`=(2xx7)/(2xx2xx6)`

`=7/12`

\(\dfrac{3}{4}\times\dfrac{8}{9}\times\dfrac{15}{16}\times\dfrac{24}{25}\times\dfrac{35}{36}\)

= \(\dfrac{3\times8\times15\times24\times35}{4\times9\times16\times25\times36}\)

= \(\dfrac{3\times\left(2\times4\text{​​}\text{​​}\right)\times\left(3\times5\right)\times\left(6\times4\right)\times\left(5\times7\right)}{4\times\left(3\times3\right)\times\left(4\times4\right)\times\left(5\times5\right)\times\left(6\times6\right)}\)

=\(\dfrac{2\text{​​}\text{​​}\times3\times6\times\left(5\times7\right)}{3\times4\times5\times\left(6\times6\right)}\)

=\(\dfrac{\text{​​}\text{​​}7}{2\times6}\)= \(\dfrac{7}{12}\)

21x6+2

=21x2x3+2

=2x(21x3+1)

=2x(63+1)

=2x64

=128

128 nha bn

21x6+2=128

k mk nha

`@` `\text {Ans}`

`\downarrow`

`(25 \times 35) \times 40`

`= 25 \times 40 \times 35`

`= 1000 \times 35`

`= 35000`

`(25×35)×40`

`=25×35×40`

`=(25×40)×35`

`=1000×35`

`=35000`

a, 25+35+76+65+22
=(65+35)+(76+22)+25
=100+100+25
=225
c , 78-23-25
=78-(23+25)
=78-48
=30
a , x-45=20 
x=20+45
x=65
b , 45 - x=20
     x =45-20
     x= 25

Bài 2: 

a: Ta có: x-45=20

nên x=65

b: Ta có: 45-x=20

nên x=25

=  225.55 +  225.55

=  451.1 

a)\(65.3,47+3,47.65\)
\(=65.\left(3,47+3,47\right)\)
\(=65.6,94\)
\(=451,1\)

\(65\times\left(3,47+3,47\right)=65\times6,94=451,1\)

Toán lớp 5

25.83-10>31.26+10

32.53-31<53.31+32

theo mình dấu chấm là dấu nhân đó nhé!

Đáp án : \(\frac{19}{10}\)

a: \(78\cdot82=80^2-4=6400-4=6396\)

b: \(45^2+90\cdot55+55^2=100^2=10000\)

`30 xx 25 xx 7 xx8`

`=(30 xx7) xx (25xx8)`

`=210 xx200`

`=42000`

`----`

`75 xx 8 xx 12 xx 14`

`=(75xx8) xx(12xx14)`

`=600xx168`

`=100800`

\(a.30\times25\times7\times8=\left(30\times7\right)\times\left(25\times8\right)=210\times200=42000\)

\(b.75\times8\times12\times14=\left(75\times12\right)\times\left(8\times14\right)=900\times112=100800\)

\(a,30.25.7.8\\ =\left(30.7\right).\left(25.8\right)\\ =210.200\\ =42000\\ b,75.8.12.14\\ =\left(75.12\right).\left(8.14\right)\\ =900.112\\ =100800\)