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0,1,2,3,4,5,6,7,8,9 from these numbers make seven digit numbers which does not change on reversing the order of digits will be (a)10000 (b)9000 (c)9910 (d)9870

0,1,2,3,4,5,6,7,8,9 from these numbers make seven digit numbers which does not change on reversing the order of digits will be
(a)10000
(b)9000
(c)9910
(d)9870

Grade:11

2 Answers

Arnab Das
18 Points
11 years ago

there are total 10 digits given. as in unit's place 0 can't sit therefore 1's place can be filled up in  9C1  ways i.e. 9 ways. again since repetition is allowed thus we can put any digit from the given ones in 10's, 100's, 1000,s place. thus in  10C1  for each place. now the number must be a palindrome . so there is no chance to select another digits for 10000's, 100000's and 1000000's place. so the required type no. can be formed in  9.10.10.10=9000 ways. ans. (b)

Askiitians Expert Sahil Arora - IITD
19 Points
11 years ago

Dear Piyushre

We have to fill first four digits and other three will automatically be fixed.

since 0 canot be in the first place.we have 9 choices for first place and 10 choices for next three places and one choice for the other places.

so total no.=9*10*10*10*1*1*1=9000

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Sahil Arora

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