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(#M40040160) TCS Numerical Ability question permutation and combinations Keep an EYE

i started writing 4 digit number, how many times i had written 2???/

Asked In TCS amit vijayvargiya (10 years ago)

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AARJU GANGWAR  (10 years ago)

option (d) this is absolutely correct
total no. of 4 digit nos are 9000(b/w 1000 and 9999).
consider the case where the nos contain no 2 in it.
so units place can be filled in 9 ways(0,1,3,4,5,6,7,8,9)
similarly,tenth place in 9 ways
hundredth place in 9 ways
thousands place can be filled in 8 ways only(because 0 cannot come)
so total nos are (9000-(8*9*9*9))=3168

Is this solution Helpfull? Yes (30) | No (4)  

Puja   (10 years ago)

if we take 2 at unit place then we can arrange the digits at thousand place with 9 ways(1,2,3,4,5,6,7,8,9)
lly, at hundred place we can arrange the digits in 10 ways(0,1,2,3,4,5,6,7,8,9)
lly,at tenth place we can arrange the digits in 10 ways(0,1,2,3,4,5,6,7,8,9).
so we have (9*10*10)ways= 900ways

in second case taking 2 at tenth place we have
Number of 2‘s at tenths place(1000 to 9999)=900

in third case taking 2 at hundredth place we have
Number of 2‘s at hundreds place(1000 to 9999)=900

in fourth case taking 2 at thousands place we have
Number of 2‘s at thousands place(1000 to 9999)=1000

therefore total number of 2‘s =(900+900+900+1000)=3700ans

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AARJU GANGWAR  (10 years ago)

If Question is How many times we will write 2 then answer is 3700
And, If Question is how many number have the number 2 in it then answer is 3168

Is this solution Helpfull? Yes (10) | No (1)  

shakshijain  (10 years ago)

as a four digit number the possibility of 2 at unit digit becomes 10*10*9 , because we can arrange the numbers as as from 0 to 9.
similarly as from the tenth digit the possibility of getting 2 becomes 10*10*9 which becomes again 900,
as same for the hundreth place the number becomes 900,
now coming for the thousands place the number becomes 10*10*10,
the total becomes 900+900+900+1000=3700

Is this solution Helpfull? Yes (5) | No (7)  

mounika  (10 years ago)

3168
9000-5832

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Trishla kapoor  (10 years ago)

2 at unit place from (1000-9999)=900
2 at tens place from (1000-9999)=900
2 " hundredth place from (1000-9999)=900
" " thousand place (1000-9999)=1000

total=900+900+900+1000=3700

Is this solution Helpfull? Yes (2) | No (1)  

Puja Dutta  (10 years ago)

2 occurs 3168 tymes in 4 digit numbers

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Amit  (10 years ago)

1000 times(Ans)
Explanation-
Number is of the form (2---)
1st place only 2 can come
2nd place 10 digits can come
3rd place 10 digits can come
4th place 10 digit can come
hence 10*10*10=1000

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Anushka  (10 years ago)

ans=2080
no.of 2 in unit place=90
no.of 2 in tens place=90
no.of 2 in hundred place=900
no.of 2 in thousand place=1000
hence total no.of 2= 90+90+900+1000=2080

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dilip yadav  (10 years ago)

Ans.after 2 we have 3 places, in this 3 places we can put digit from 0 to 9 means total 10 digit.
10*10*10=1000 using permutation and combination
alternative way====
from starting with 2 we have number 2000 to 2999 because given first digit must be 2 so
according AP first a=2000 last number l=2999 and d=1 then
l=a+(n-1)d
2999=2000+(n-1)1
2999-2000=n-1
999+1=n
ans n=1000

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Puja   (10 years ago)

please anyone explain and write solution of this question as soon....

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Anushka  (10 years ago)

there is possibility of coming no.2222 in all the four cases then the same no. 2 will be counted 4 times extra..how to egnore it?? @PUJA

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Varun  (10 years ago)

the ans is
9*10*10*1=900
9*10*1*10=900
9*1*10*10=900
1*10*10*10=1000

3700

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