55555+5+55555+55+5555+5+55555+5555555555555555+5555+555555=555555556.10^15

kq của phép tính trên = 5555555556288950.

5.555555556\(\times10^{15}\)

\(5+55+555+5555+55555=61725\)

5 + 55 + 555 + 5555 + 55555 = 61725

5 + 55 + 555 + 5555 + 55555 = 61725 k nha

\(5555:55=101\)

5555:55=101

5555:55= 101

nha bạn 

=55555.....5555555.

(Có 555...555 số 5)

5+55+555+5555/7+77+777+7777

= 10039.5714286

Học tốt !!! Chúc bn luôn may mắn !!!

Mình mong bn hãy !!!

Thanks !!!

Ta có \(\frac{5+55+555+5555}{7+77+777+7777}\)

\(=\frac{5.\left(1+11+111+1111\right)}{7.\left(1+11+111+1111\right)}\)

\(=\frac{5}{7}\)

Vậy \(\frac{5+55+555+5555}{7+77+777+7777}=\frac{5}{7}\)

thank you very much

\(=\frac{5}{7}\)

Cho mk xin cái li ke

a, = 5x1+5x11+5x111+5x1111

=5 x (1+11+111+1111)

=5 x 1234

=6170

b, giống câu trên.

\(\frac{5.\left(1+11+111+1111\right)}{7.\left(1+11+111+1111\right)}=\frac{5}{7}\)

k cho mik nha

Đáp án C.

Ta có S n = 5 ( 1 + 11 + 111 + … 111 … 1 ⏟ n sè 1 )  

Tính A n = 1 + 11 + 111 + … + 111 … 1 ⏟ n sè 1  

Xét:

u 1 = 1 u 2 = 1 + 10 u 3 = 1 + 10 + 10 2 u 4 = 1 + 10 + 10 2 + 10 3 ⋮ u n = 1 + 10 + 10 2 + 10 3 + … + 10 n − 1

A n = n .1 + ( n − 1 ) 10 + ( n − 2 ) .10 2 + … + n − ( n − 1 ) 10 n − 1

⇒ 10 A n = 10 n + 10 2 ( n − 1 ) + 10 3 ( n − 2 ) + … + n − ( n − 1 ) 10 n

( 2 ) - ( 1 ) ⇒ 9 A n = − n + 10 + 10 2 + 10 3 + … + 10 n − 1 + 10 n = − n + 10. 1 − 10 n 1 − 10

⇒ A n = 1 9 . 10 n + 1 − 10 9 − n 9 ⇒ S 2018 = 5. A 2018 = 5 9 10 2019 − 10 9 − 2018 8