Dear Readers, Welcome to Numbers Formulas Objective Questions have been designed specially to get you acquainted with the nature of questions you may encounter during your Job interview for the subject of Numbers Formulas MCQs. These objective type Numbers Formulas questions are very important for campus placement test and job interviews. As per my experience good interviewers hardly plan to ask any particular question during your Job interview and these model questions are asked in the Banks, SSC, Railways, Postal and many Govt Jobs.
1. Natural Numbers :
Counting numbers 1, 2, 3, 4, 5, .. are called natural numbers.
2. whole Numbers :
All counting numbers together with zero form the set of whole numbers.
3. Some Important Formulas :
I. ( 1 + 2 + 3 + .....+ n) = n (n + 1 ) / 2
II. (1 2 + 22 + 32 + ..... + n2) = n ( n + 1 ) (2n + 1) / 6
III. (1 3 + 23 + 33 + ..... + n3) = n2 (n + 1)2 / 4
4. Even Numbers:
A Number Divisible by 2 is called an even number, such as 2,4,6,8,10....etc
5. Odd Numbers:
A Number not divisible by 2 is called an odd number, such as 1,3,5,7,9,11..... etc
6. Prime Number:
A Number, other than 1 is called a prime number, if it is divisible by 1 and itself only.
7. Some Basic Formulas:
i. (a + b)(a - b) = (a2 - b2)
ii. (a + b)2 = (a2 + b2 + 2ab)
iii. (a - b)2 = (a2 + b2 - 2ab)
iv. (a + b + c)2 = a2 + b2 + c2 + 2(ab + bc + ca)
v. (a3 + b3) = (a + b)(a2 - ab + b2)
vi. (a3 - b3) = (a - b)(a2 + ab + b2)
vii. (a3 + b3 + c3 - 3abc) = (a + b + c)(a2 + b2 + c2 - ab - bc - ac)
viii. When a + b + c = 0, then a3 + b3 + c3 = 3abc.