Question 1204335
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The total set is 40 + 18 = 58 calculators.


The probability that no one of 4 calculators is defective is

    {{{(40/58)*(39/57)*(38/56)*(37/55)}}} = 0.215405284.



The probability that at least one calculator is defective is the complement to it

    P = 1 - {{{(40/58)*(39/57)*(38/56)*(37/55)}}} = 1 - 0.215405284 = 0.784594716.


<U>ANSWER</U>.  The probability that at least one calculator is defective is  0.7846  (rounded).
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Solved.