1.

Find the sum of the sequence 8, 88, 888, 8888, … to n terms.

Answer»

Sn = 8 + 88 + 888 + ……………… 

= 8[1 + 11 + 111 + ………….. ] 

= 8/9(9 + 99 + 999 + ……nth term) 

= 8/9[(10 – 1)+(102 – 1]+ ………] 

= 8/9[10(102 – 1) ] [(10 + 102 + 103 + ……. nth term) – (1 + 1 + 1 + …..)] 



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