Latest TCS Aptitude Question SOLUTION: A person starts writing all 4 digit numbers .How many times had he written the digit 3?

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A person starts writing all 4 digit numbers .How many times had he written the digit 3?

Asked In TCS Raja (10 years ago)

Solved Sunny Kumar Read Solution (6)

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ANURAG VERMA  (10 years ago)

3700
_ _ _ 3 = 9*10*10
_ _ 3 _ = 9*10*10
_ 3 _ _ = 9*10*10
3 _ _ _ = 10*10*10

900+900+900+1000=3700

Is this solution Helpfull? Yes (29) | No (7)  

Sunny Kumar  (10 years ago)

case 1:no of 4 digit nos with one 3 digit=4C1*9*9*9=2916
case 2:no of 4 digit nos with two 3 digit=4C2*9*9=486
case3:no of 4 digit nos with three 3 digit=4C3*9=36
case 4:no of 4 digit nos with one 4 digit=1
No of times we typed digit 3=(2916*1)+(486*2)+(36*3)+(1*1)=3997(ans)

Is this solution Helpfull? Yes (26) | No (8)  

uday  (9 years ago)

Number of 3's at units place(1000 to 9999)=900
Number of 3's at tenths place(1000 to 9999)=900
Number of 3's at hundreds place(1000 to 9999)=900
Number of 3's at thousands place(1000 to 9999)=1000

therefore total number of 3's =(900+900+900+1000)=3700

Is this solution Helpfull? Yes (4) | No   

arsalan  (9 years ago)

case 1:no of 4 digit nos with one 3 digit=4C1*9*9*9=2916
case 2:no of 4 digit nos with two 3 digit=4C2*9*9=486
case3:no of 4 digit nos with three 3 digit=4C3*9=36
case 4:no of 4 digit nos with four 3 digit=4C4=1
No of times we typed digit 3=(2916*1)+(486*2)+(36*3)+(1*4)=4000(ans)

Is this solution Helpfull? Yes (2) | No (4)  

ajit jha  (10 years ago)

3 is 0-99 is 20
3 is 100-999 is 100
3 is 1000-9999 is 1000

ans 1120

Is this solution Helpfull? Yes (1) | No (11)  

sarika kumari  (9 years ago)

ans is 3699

Is this solution Helpfull? Yes | No (4)  

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