Question

Q.23

23. Raj wanted to type the first 200 natural numbers, how many times does he have to press the keys
(1) 489
(2) 492
(3) 400
(4) 365

Answer 1

9(1) ....9 one digit numbers
+ 90(2)....90 two digit numbers
+ 101(3)....101 three digit numbers
=492

Answer 2

Answer:

Total number of times the key will be pressed = 492          

Step-by-step explanation:

There are 9 one digit natural numbers that are 1 to 9 = 9

Number of digits in the natural numbers 1 to 9 = 1

So, Number of times the key will be pressed = 9 × 1 = 9

Number of two digit numbers : 10 to 99 = 90

Number of digits in the natural numbers from 10 to 99 = 2

So, number of times the key will be pressed to type the two digit numbers = 90 × 2 = 180

Number of three digit numbers : 100 to 200 = 101

Number of digits in the natural numbers from 100 to 200 = 3

So, number of times the key will be pressed to type the three digit numbers = 101 × 3 = 303

Total number of times the key will be pressed = 9 + 180 + 303

                                                                                = 492