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I GAVE MOCK TEST 2 AND I HAVE DOUBT IN QUESTION 18
Answers (1)
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A person starts typing the numbers from 1 to 1999. He press the keys total ‘n’ number of times. The value of n is:
Are you talking about this question ??? If yes then in this problem we have to find out the total number of times a key is hit to write all the numbers from 1 to 1999
These 1999 numbers can be grouped into 4 categories based on the number of digits
A - 1 digit number number
They are total 9 in number ( 1 to 9 )
B - 2 digit numbers
They are in all 90 in number ( 10 - 99 )
C 3 digit numbers
They are in all 900 in number ( 100 - 999)
D - 4 digit numbers
They are in all 1000 in number ( 1000 - 1999)
now if we want to type 1 digit number then we have to hit one key
if we want to type a 2 digit number , then we have to hit two keys.
if we want to type a 3 digit number , then we have to hity three keys
if we want to type a 4 digit number then we have to hit four keys
Total number of times = 1 x 9 + 90 x 2 + 900 x 3 + 1000 x 4 = 9 + 180 + 2700 + 4000 = 6889