JMO, numbers

How many keystrokes are needed to type numbers from 1 to 2000 on a standard keyboard?



Answer:

for the first 9 numbers, no. of keystrokes = 9
from 10 to 99, the next 90 numbers, no. of keystrokes = 90 x 2 =180
from 100 to 999 the next 900 numbers, no. of key strokes = 900 x 3 = 2700
from 1000 to 2000, thee next (2000 - 1000 + 1 = 1001), no. of key strokes = 1001 x 4 = 4004

So, total number of keystrokes = 9 + 180 + 2700 + 4004 =       6893