MHT CET 2018 Math Solved Paper

(b) 9 +99 + 999 + ........upto 10 terms
= (10 - 1) + (100 - 1 ) + (1000 - 1) + ........upto 10 terms
= (10 + 100 + 1000 + .........upto 10 terms) - (1 + 1+ ... upto 10 times)
=

10[(10)10−1]

10−1

−10
=

10(1010−1)

9

−10 =

1011−10−90

9

=

1011−100

9

=

100(109−1)

9