Banking Exam Notes

Tests of divisibility -  Divisibility by 2: A number is divisible by 2 if its unit digit is zero or an even number. Example: 248, 130 Divisibility by 3: A number is divisible by 3 if the sum of its digit is divisible by 3. Example: 273 ® 2 + 7 + 3 = 12. 12 is divisible by 3, hence 273 is divisible by 3. Divisibility by 4: A number is divisible by 4 if the number formed by its last two digits is divisible by 4. Example: 236784 Here, 84 is divisible by 4, hence 236784 is divisible by 4. Divisibility by 5: A number is divisible by 5 if the number or its unit digit is either 5 or 0. Example: 115, 240, etc. Divisibility by 6: A number is divisible by 6 if it is divisible by both 2 and 3. Example: 318, 396, etc. Divisibility by 8: A number is divisible by 8 if the number formed by its last 3 digit is divisible by 8. Example: 23816. Here, 816 is divisible by 8, hence 23816 is divisible by 8. Divisibility by 9: A number is divisible by 9 if the sum of all its digits is divisible by 9. Exam...

This post forms a basis of many other topics in quantitative aptitude . Let us begin by understanding various types of numbers. (1) Natural Numbers: All the counting numbers are called natural number. Example: 1, 2, 3, 4, 5, ...... (a) Even Numbers: The numbers which are exactly divisible by 2 are called even numbers. Example: 2, 4, 6, 8, ... (b) Odd Numbers: The numbers which leave a remainder 1 when divided by 2 are called odd numbers. Example: 1, 3, 5, 7, .... (c) Prime Numbers: If a number is not divisible by any other number except 1 and itself, it is called a prime number. Example: 2, 3, 5, 7, 11, .... Co-primes ® Two numbers which have no common factor between them except 1 are said to be co-prime to each other. The two numbers individually may be prime or composite. Example: 13 and 29 are co-primes. (d) Composite Numbers: Numbers which are divisible by other numbers along with 1 and itself are called composite numbers. Example: 4, 6, 8, 9, 10, ..... The number 1 is neither prim...