2016 · Q27
A device can write 100 digits in 1 minute. It starts writing natural numbers. The device is stopped after running for half an hour. It is found that the last number it was writing is incomplete. The number is:
general-mental-abilityquantitative-aptitude
- A3000
- B3001
- C1026
- D1027
Explanation
In 30 minutes the device writes 30 x 100 = 3000 digits. Numbers 1-9 use 9 digits and 10-99 use 180 digits (189 total); 100-999 use 2700 digits (2889 total). The remaining 111 digits cover 27 four-digit numbers (108 digits: 1000-1026), leaving 3 digits, which begin but cannot complete 1027. Hence the incomplete number being written is 1027.