9900 : 36 - 15 x 11 

= 275 - 165

= 110

9700 : 100 + 36 x 12

= 97 + 432

= 529

( 15792 : 336 ) x 5 + 27 x 11

= 47 x 5 + 297

= 235 + 297

= 532

( 160 x 5 - 25 x 4 ) : 4

= ( 800 - 100 ) : 4

= 700 : 4

= 175

1036 + 64 x 52 - 1827

= 1036 + 3328 - 1827

= 4364 - 1827

= 2537

215 . 869 + 215 . 14 

= 215 . ( 869 + 14 ) 

= 215 . 883 

= 189945 

9900:36-15x11= 110 ;   

9700:100+36x12= 529 ;   

( 15792 : 336 ) x 5 + 27 x 11= 532

(160 x 5 – 25 x 4) : 4= 175

;   1036 + 64 x 52 – 1827 = 2537

   215 x 86 + 215 x 14= 21500

12 054 : (15 + 67) = 147

;   53 x 128 - 43 x 128 = 1280

;   29150 - 136 x 201= 1814

các pác trình bày tình bước ra giúp cháu cx đc ạ

1748.32+9900/495

=1748.32+20

=55 936 + 20

=55 956

A = \(\dfrac{1}{12}\)+ \(\dfrac{1}{20}\)+ \(\dfrac{1}{30}\)+...+\(\dfrac{1}{9900}\)

A = \(\dfrac{1}{3\times4}\)+ \(\dfrac{1}{4\times5}+\dfrac{1}{5\times6}+...+\dfrac{1}{99\times100}\)

A = \(\dfrac{1}{3}-\dfrac{1}{4}+\dfrac{1}{4}-\dfrac{1}{5}+\dfrac{1}{5}-\dfrac{1}{6}+...+\dfrac{1}{99}-\dfrac{1}{100}\)

A = \(\dfrac{1}{3}\) - \(\dfrac{1}{100}\)

A = \(\dfrac{97}{300}\) 

Lời giải:

Gọi tổng trên là $A$

$A=\frac{1}{3.4}+\frac{1}{4.5}+\frac{1}{5.6}+....+\frac{1}{99.100}$

$=\frac{4-3}{3.4}+\frac{5-4}{4.5}+\frac{6-5}{5.6}+...+\frac{100-99}{99.100}$

$=\frac{1}{3}-\frac{1}{4}+\frac{1}{4}-\frac{1}{5}+....+\frac{1}{99}-\frac{1}{100}$

$=\frac{1}{3}-\frac{1}{100}=\frac{97}{300}$

`A=1/2+1/6+1/12+1/20+1/30+...+1/9900`

`=1/(1xx2)+1/(2xx3)+1/(3xx4)+1/(4xx5)+1/(5xx6)+...+1/(99xx100)`

`=1/1-1/2+1/2-1/3+1/3-1/4+1/4-1/5+1/5-1/6+...+1/99-1/100`

`=1/1-1/100`

`=100/100-1/100`

`=99/100`

$A=1/2+1/6+1/12+1/20+1/30+...+1/9900$

$=1/(1xx2)+1/(2xx3)+1/(3xx4)+1/(4xx5)+1/(5xx6)+...+1/(99xx100)$

$=1/1-1/2+1/2-1/3+1/3-1/4+1/4-1/5+1/5-1/6+...+1/99-1/100$

$=1/1-1/100$

$=100/100-1/100$

$=99/100$

a) 397,5 : 7,5 x 10,5 =53 x 10,5 = 556,5
b) 36 : 15 x 5,4 = 2,4 x 5,4 = 12,96

a. 53 x 10,5

= 556,5

b. 2,4 x 5,4

= 12,96

a)\(397,5\div7,5\times10,5\)

=53 \(\times\) 10,5

=556.5

b)36 \(\div\) 15 \(\times\) 5,4

=2,4 \(\times\) 5,4

=12,96

ta có: 
1/2+1/6+...+1/9900 
=1/1.2+1/2.3...+1/99.100 
=1-1/2+1/2-1/3+1/3-...+1/99-1/100 
=1-1/100 
=99/100

\(A=\frac{1}{2}+\frac{1}{6}+\cdot\cdot\cdot+\frac{1}{9900}\)

\(A=\frac{1}{1\times2}+\frac{1}{2\times3}+\cdot\cdot\cdot+\frac{1}{99\times100}\)

\(A=1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\cdot\cdot\cdot+\frac{1}{99}-\frac{1}{100}\)

\(A=1-\frac{1}{100}\)

\(A=\frac{99}{100}\)

\(A=\frac{1}{2}+\frac{1}{6}+\frac{1}{12}+\frac{1}{20}+\frac{1}{30}+...+\frac{1}{9900}\)

\(A=\frac{1}{1.2}+\frac{1}{2.3}+\frac{1}{3.4}+\frac{1}{4.5}+\frac{1}{5.6}+...+\frac{1}{99.100}\)

\(A=\frac{1}{1}-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+\frac{1}{4}-\frac{1}{5}+\frac{1}{5}-\frac{1}{6}+...+\frac{1}{99}-\frac{1}{100}\)

\(A=\frac{1}{1}-\frac{1}{100}\)

\(A=\frac{99}{100}\)

a; 54 : 72 x 18 : 15

= 0,75 x 18 : 15

= 0,75 x 1,2

= 0,9 

b, 25 : 8 x 36 : 50

= (25  : 50) x (36 : 8)

= 0,5 x 4,5

= 2,25 

= 

a. = 0,75 x 18 : 15

    = 0,75  x 1,2

   = 0, 9

b. = ( 25 : 50 ) x ( 36 : 8)

= 0, 5 x 4,5

= 2, 25

\(25\cdot16-12\cdot55\)

\(=400-660\)

\(=-260\)

\(---\)

\(930:15-320:5+196\)

\(=62-64+196\)

\(=-2+196\)

\(=194\)

\(---\)

\(4\cdot5^2-81:3^2\)

\(=4\cdot25-81:9\)

\(=100-9\)

\(=91\)

\(---\)

\(7^6:7^4+3^4:3^2-3^7:3^6\)

\(=7^2+3^2-3\)

\(=49+9-3\)

\(=58-3\)

\(=55\)

#\(Toru\)