Aptitude 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.