A) 63
B) 65
C) 61
D) 60
Correct Answer: A
Solution :
[a] Total no. of ways to invite one or more of his friends \[{{=}^{6}}{{C}_{0}}{{+}^{6}}{{C}_{1}}{{+}^{6}}{{C}_{2}}{{+}^{6}}{{C}_{3}}{{+}^{6}}{{C}_{4}}{{+}^{6}}{{C}_{5}}{{+}^{6}}{{C}_{6}}\] \[=1+6+15+20+15+6+1=63\] Hence, option [a] is correct.
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