Differentiation Silly Question

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Let x={a₁,a₂,a₃,......,a₆} and y={b₁,b₂,b₃}. Then number of functions f from x to y such that it is onto and there are exactly three elements in x such that f(x) =b₁, is
a) 75 b) 90
c) 100 d) 120

Ans: (d)

Please explain how to get answer?
I am not getting by formula.

#Mathematics #Calculus

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Aditya Bhutra ·2012-04-02 12:06:31

ways of choosing 3 elements of set x ( for f(x) =b1) = ⁶C₃ = 20

now we are left with x={A,B,C} and y={M,N}

number of onto functions in this case = 2*³C₂*1 = 6

thus total number of functions = 20*6 =120

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Athenes Analyst ·2012-04-02 14:00:44

Thanks Aditya...I got this.. :)

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Differentiation Silly Question

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