At a local school, there are 17 girls and 21 boys in seventh grade and 14 girls and 12 boys in eighth grade. The school principal randomly selects an eighth grader and a seventh grader for a citywide competition. What is the probability that the students she selects are both boys? Write your answer as a fraction in lowest terms.
Please Explain how to solve this problem in layman's terms.
2007-05-30 11:53:24 · 2 answers · asked by Thegrinch57 1 in Science & Mathematics ➔ Mathematics
i will assume that it doesnt matter who the principal picks first, the 7th grader or the eight grader.
the number of ways that a boy will be picked from the 7th graders is 21 from 17+21 = 38. the probability is 21/38
the number of ways that a boy will be picked from the 8th graders is 12 from 14+12 = 26. the probability is 12/26
so the probability that the students selected will be both boys is (21/38)(12/26) = (21* 12)/(38 * 26) = 252/ 988 or 63/247
in lowest terms
2007-05-30 23:39:41 · answer #1 · answered by TENBONG 3 · 0⤊ 0⤋
P(2 boys) = (21/(17 + 21))(12/(12 + 14)) = 21*3/(19*13) = 63/247
2007-05-30 19:00:40 · answer #2 · answered by Helmut 7 · 0⤊ 0⤋