Permutation Combination Question 9

Question 9 - 29 January - Shift 2

The number of 3 digit numbers, that are divisible by either 3 or 4 but not divisible by 48 , is

(1) 472

(2) 432

(3) 507

(4) 400

Show Answer

Answer: (2)

Solution:

Formula: Divisibility of numbers

Total 3 digit number $=900$

Divisible by $3=300 \quad$ (Using $\frac{900}{3}=300$ )

Divisible by $4=225$ (Using $\frac{900}{4}=225$ )

Divisible by $3 ; & ; 4=108, \ldots$

$ \text{ (Using } \frac{900}{12}=75) $

Number divisible by either 3 or 4

$ =300+2250-75=450 $

We have to remove divisible by 48 ,

$144,192, \ldots . ., 18$ terms

Required number of numbers $=450-18=432$