This GMAT problem solving question tests concepts in counting methods.

#### Question: How many keystrokes are needed to type numbers from 1 to 1000?

- 3001
- 2893
- 2704
- 2890
- None of these

#### Video Explanation

Scroll for explanatory answer text#### Explanatory Answer

While typing numbers from 1 to 1000, there are 9 single digit numbers: from 1 to 9.

Each of these numbers 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, 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, 2700 keystrokes to type the 3-digit numbers.

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

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

Choice B is the correct answer.

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