Question 1161251
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9 boys + 12 girls = 21 students total 

P(out of 6 students selected at random, all are boys) = 
    (9/21)(8/20)(7/19)(6/18)(5/17)(4/16) = 60480 / 39070080

     = 1/646 or approximately 0.00155 (0.155%)