Latest TCS Aptitude Question SOLUTION: A person writing all 4 digit number. How many times he will use 2?

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A person writing all 4 digit number. How many times he will use 2?

Asked In TCS aryan vyas (8 years ago)

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Puja Rani  (8 years ago)

if select any no. from 0-9 the probability of each digit=1/10,consider no. be wxyz
probability of 2 at w=1/9
prob. of 2 at x=1/10
prob. of 2 at y=1/10
prob. of 2 at z=1/10
so, 1/9+1/10+1/10+1/10=37/90
total no. of 4 digit no. = 9*10*10*10=9000
so, totalno. of 2=(37*9000)/90=3700

Is this solution Helpfull? Yes (24) | No (2)  

Abhinav Akash  (8 years ago)

ans:3700
at 1's place=900 times
at 10's place=900 times
at 100's place=900 times
at 1000's place(from 2000 to 2999)=1000 times
total=1000+900+900+900=3700

Is this solution Helpfull? Yes (11) | No (3)  

NIKITHA BOLLINENI  (8 years ago)

total no. of four digit numbers is 9000
no of digits that does not contain 2 is
thousands place can be filled in 8 ways
hundreds place can be filled in 9 ways
ten's place in 9 ways
units place in 9 ways
8*9*9*9=5832
now no of digits that contain 2 is 9000-5832=3168

Is this solution Helpfull? Yes (5) | No   

Vishal Kumar  (8 years ago)

3700 time we use 2 to write all 4 digit number.
at the unit place 2 comes 900 times
at the tenth place 2 comes 900 times
at the hundred th place 2 comes 900 times
at the last thousend th place 2 will comes 1000 time so
that 900*3+1000=3700 is the final answer..!!!

Is this solution Helpfull? Yes (3) | No (1)  

Niharika Gupta  (8 years ago)

1133 is the answer

Is this solution Helpfull? Yes (2) | No (5)  

N Murali Krishna   (8 years ago)

3811 ways.....we can use two 2s also and three 2s too......consider that way too

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