-1300

-3600

1544

13.(-87)+(-13).13= 13.(-87+(-13))

                        = 13.(-100)

                        =-1300

( 13 * 78 + 13 * 22 ) + ( 87 * 55 + 87 * 45 )

= 13 * ( 78 + 22 ) + 87 * ( 55 + 45 )

= 13 *    100   +    87 *   100

= 1300   + 8700

=      10 000

112-45+5x=87
45+5x=112-87
5x=25-45
x=-25:5
x=_5

99 + 87 + 99 + 13 + 99 + 45

= ( 99 + 99 + 99 ) + ( 87 + 13 ) + 45

= 297 + 100 + 45

= 397 + 45

= 442

99+87+99+13+99+45
=(99+99+99)+(87+13)+45
=297+100+45
=442

4) 121

5) - 32

6) 48

7) - 137

8) - 280

9) - 36

10) 42

4) 41

5) -32

6)  48

7) -137

8) -280

9) -36

10) 42

a. 27 x (121-87-(16))

= 27 x 50 

= 1350 

b. (-37)x (17+23-46)

=-37 x -6 

= 222 

c. 41 x (-18-81-1) 

= 41 x -100 

= -4100 

d. 1080 + 120 

= 1200

a)=22

b)=17

c)=15

d)=37

e)=96

f)=10

450:27

a)45.(13+78)+9.(87+22).5

=45.91+(9.5).109

=45.91+45.109

=45.(91+109)

=45.200

=9000

b) 16.(27+75)+8.(53+25).2

=16.102+(8.2).78

=16.102+16.78

=16.(102+78)

=16.180

=2880

cai bai nay minh thay

quen quen nhung lai ko nghi ra

chu!

chuc bn hoc gioi1

Ta có : \(\frac{1}{1000}+\frac{13}{1000}+\frac{25}{1000}+.....+\frac{85}{1000}+\frac{97}{1000}\)

\(=\frac{1+13+25+......+85+97}{1000}\)

\(=\frac{441}{1000}\)