a bag has 1 , 3 , 5 , 7 , 9,11 and 13 cm sticks . find the probability that they they will form a triangle if 3 sticks are drawn ?
explanation : total cases : = 7 c 3 = 35 favourable cases : ( 3 , 5,7 ) , ( 3 , 7,9 ) , ( 3 , 9,11 ) , ( 3 , 11,13 ) , ( 5 , 7,9 ) , ( 5 , 7,11 ) , ( 5 , 9,11 ) , ( 5 , 9,13 ) , ( 5 , 11,13 ) , ( 7 , 9,11 ) , ( 7 , 9,13 ) , ( 7 , 11,13 ) , ( 9 , 11,13 ) = total 13 . [ others are rejected because to form a triangle it is necessary that the sum of 2 small sides must be greater than the third greatest side . ] hence ( a ) is correct answer . answer : a
divide(add(7, permutation(3, 7)), choose(7, 3))