Math, asked by rsudhanshu83, 6 months ago

find the number of different possible A.P's of 5 terms from first 20 natural number....solve it guys​

Answers

Answered by ratamrajesh
2

Step-by-step explanation:

Total ways of selecting consecutive no.s are (1,2,3,4),(2,3,4,5),(3,4,5,6),........,(17,18,19,20)=17 possible ways

Total ways of selecting non consecutive no.s = Total ways of selecting - Total ways of selecting consecutive no.s

=

20

C

4

−17

=19×15×17−17

=17(19×15−1)=284×17

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