KVPY 2020-21 SA Exam Previous Papers

Question : 8 of 80

Marks: +1, -0

If the integers from 1 to 2021 are written as a single integer like 123 … 91011 … 20202021, then the 2021

^{\st}

digit(counted from the left) in the resulting number is

Validate

Solution:

Total number of digits used till 99 = 9 + 90 × 2 = 189
The digits use in next 610 three digit numbers = 1830
∴ Total digit used till the number 710 = 189 + 1830 = 2019
Next three digits are 711
∴ 2021

^{\st}

digit is 1.

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