Hi Friends,

I have started a new series of concepts and their applications in SSC and CAT exams. This series is named as -Bond series. In these sessions, we will discuss the questions asked in SSC CGL mains 2017 and analyse the concept with questions asked inprevious CAT and SSC exams.

Concept

For given n different digits a,b,c........n; the sum of the digit at the unit place of all different numbers formed is = (n-1)!(a+b+c........n)= (n-1)! (sum of the digits)

Case Study

Find the number of three digit numbers having:

• All three digit prime and distinct.
• All three digits odd.
• The ten's place digit less than the unit's place digit.
• The ten's place digit less than both the hundred's place and unit's place digit.

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