# Moderate Number System Solved QuestionAptitude Discussion

 Q. How many keystrokes are needed to type numbers from 1 to 1000 on a standard keyboard?
 ✖ A. 3001 ✔ B. 2893 ✖ C. 2704 ✖ D. 2890

Solution:
Option(B) is correct

While typing numbers from 1 to 1000, you have 9 single digit numbers from 1 to 9. Each of them requires one keystroke. That is 9 key strokes.

There are 90 two-digit numbers, from 10 to 99. Each of these numbers requires 2 keystrokes. Therefore, one requires 180 keystrokes to type the 2 digit numbers.

There are 900 three-digit numbers, from 100 to 999. Each of these numbers requires 3 keystrokes. Therefore, one requires 2700 keystrokes to type these 3 digit numbers.

Then 1000 is a four-digit number which requires 4 keystrokes.

Totally, therefore, one requires $9 + 180 + 2700 + 4 =$ 2893 keystrokes.