SSC Exam Quantitative Aptitude Study Material: A conceptual guide for Combination

SSC is well known for the recruitment of Group ‘B’ and ‘C’ posts under the Ministries/Departments in The Government of India. SSC organizes various examinations like Combined Graduate Level examination, Combine Higher Secondary Level, Stenographer and for SI/DP/CAPF, etc., throughout the year having almost the same Exam Pattern. The Exam paper is comprised of basically 4 subjects.

             a. General Intelligence & Reasoning

             b. English language & Comprehension

             c. Quantitative Aptitude

             d. General knowledge

For more detail, click the link given below.

SSC SI, CAPF & ASI Exam 2015: Exam Pattern

SSC Combined Higher Secondary Level (10+2) Exam 2014: Exam Pattern

SSC JHT & Hindi Pradhyapak and Sr. / Jr. Translators Exam 2014: Exam Scheme & Syllabus

SSC Stenographer 2016: Take a look of Exam Pattern, Syllabus and Selection Procedure

So, Jagranjosh.com has introduced a brief plan for revising topics at the time of examination. In this article, Combination which sometimes appear more difficult to understand in terms of making combinations & collections.

Combination

From a given group of object each of the number of groups which are formed by taking some objects or all objects at a time without caring about the sequence of the objects is called combination. The number of combination formed by taking r objects at a time out of n object is denoted by nC_r where C expresses combination.

Restricted combination:

The combination of r object out of n objects on which p specific objects:

1. Are always included is n-pC_r-p. We have to keep aside p specific objects and to select remaining (n-p).
2. Are never included is n-pC_r . Since p specific object are never included we have to form the combination taking r obects out of (n-p) objects.

The number of ways to select some or all thing out of any number of given thing:

There are 2 ways to select anything i.e. either it will be selected or not. Therefore number of ways to select n things is 2 × 2 × …………… n times = . 2ⁿ these empty selection is also include. For non- empty selection is 2ⁿ-1.

Note: nC₁ + nC₂ +…………………………. + nC_n = 2ⁿ-1.

Difference between permutation and combination:

Suppose there are 5 objects out of which 2 have to be chosen.

So it is clear that in permutation order matters while in combination order does not matter.