Latest TCS Aptitude Question SOLUTION: How many 4 digit numbers can be made by using digits 1 to7(repetition is not allowed),if the digit 4 will always be there in the number? a. 400 b. 480 c. 360 d. 240 e. None of

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How many 4 digit numbers can be made by using digits 1 to7(repetition is not allowed),if the digit 4 will always be there in the number?

a. 400
b. 480
c. 360
d. 240
e. None of these

Asked In TCS padmapriya (10 years ago)

Unsolved Read Solution (11)

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Read Solution (11) :

Debabrata Roy Chowdhury  (10 years ago)

Ans: 480
Place 4 in all the four places one by one and arrange the rest.
4 _ _ _ = 1*6*5*4 = 120
_ 4 _ _ = 6*1*5*4 = 120
_ _ 4 _ = 6*5*1*4 = 120
_ _ _ 4 = 6*5*4*1 = 120

Total = 120*4= 480.

Is this solution Helpfull? Yes (37) | No (1)  

KOPPUROTHU PRITHVI  (10 years ago)

Ans 480
4 digit no to be formed using digits from 1 to 7 without repetition with 4 always included in the no
So we can place the digit 4 in the no in 4 ways
Remaining 6 digits need to be placed in the remaining 3 places without repetition that can be done in 6p3 ways
Therefore 6p3*4=6*5*4*4=480

Is this solution Helpfull? Yes (9) | No (2)  

chandan kumar  (10 years ago)

at unit place take 4 then total no=1*6*5*4=120
in this way 4 can occur at ten's place thousand;s place ,ten thousand's place
so there will be total 4*120 arrangement
so no=480.

Is this solution Helpfull? Yes (4) | No (1)  

Ann Mary Jolly  (10 years ago)

Ans : b)480
Since the digit 4 should be there in the no.,considering 4 at first units place,
the next place can have any digit from 1-7 other than 4 ;so 6 cases.
For each of these 6 cases, the next place can take any of the existing 5.And thus 6*5 cases.Like wise keeping 4 at units place there can be 6*5*4 = 120 possibilities.Similarly placing 4 at other 3 places,we get 4*120 = 480 no.s in total.

Is this solution Helpfull? Yes (1) | No   

Arindam Dhara  (10 years ago)

digit 4 is fixed...so for rest 3 digits we have 6 possible options without reptitation....that makes it 6c1*5c1*4c1=120.
Now the digit 4 can be placed in 4 ways, so its 4*120=480(opt B)

Is this solution Helpfull? Yes (1) | No   

shubhankar barman  (10 years ago)

Ans: 480
Place 4 in all the four places one by one and arrange the rest.
4 _ _ _ = 1*6*5*4 = 120
_ 4 _ _ = 6*1*5*4 = 120
_ _ 4 _ = 6*5*1*4 = 120
_ _ _ 4 = 6*5*4*1 = 120

Total = 120*4= 480.

Is this solution Helpfull? Yes (1) | No   

Bholanath   (10 years ago)

4*(6*5*4)=480

Is this solution Helpfull? Yes | No   

prateek  (10 years ago)

ans...120

Is this solution Helpfull? Yes | No (7)  

sireesha  (10 years ago)

ans 480
4*6*5*4=480

Is this solution Helpfull? Yes | No (1)  

Nishandini  (10 years ago)

Ans: 600
total digits=7
let us consider 4 occupies the 1st position then the possible chance is
4_ _ _
1*6*5*4=150
but 4 may come in 2 or 3 or 4th place.so 150*4=600

Is this solution Helpfull? Yes | No (5)  

Akhil Sharmaq  (10 years ago)

Ans 480
total digits=7
let us consider 4 occupies the 1st position,
4_ _ _
1*6*5*4=120
Now 4 will similarly occupy 2nd,3rd & 4th position as well,and the calculation remains the same,
so, for all 4 cases, 4*(6*5*4) = 480

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