william recorded the grade - level and instrument of everyone in the middle school school of rock…

william recorded the grade - level and instrument of everyone in the middle school school of rock below.\nseventh grade students\n|instrument|# of students|\n|--|--|\n|guitar|9|\n|bass|11|\n|drums|9|\n|keyboard|11|\neighth grade students\n|instrument|# of students|\n|--|--|\n|guitar|3|\n|bass|3|\n|drums|8|\n|keyboard|6|\nbased on these results, express the probability that a seventh grader chosen at random will play the keyboard as a fraction in simplest form.

william recorded the grade - level and instrument of everyone in the middle school school of rock below.\nseventh grade students\n|instrument|# of students|\n|--|--|\n|guitar|9|\n|bass|11|\n|drums|9|\n|keyboard|11|\neighth grade students\n|instrument|# of students|\n|--|--|\n|guitar|3|\n|bass|3|\n|drums|8|\n|keyboard|6|\nbased on these results, express the probability that a seventh grader chosen at random will play the keyboard as a fraction in simplest form.

Answer

Explanation:

Step1: Calculate total 7 - th grade students

Add the number of students for each instrument in 7 - th grade. $9 + 11+9 + 11=40$.

Step2: Identify number of 7 - th grade keyboard players

The number of 7 - th grade students who play the keyboard is 11.

Step3: Calculate the probability

The probability $P$ that a randomly - chosen 7 - th grader plays the keyboard is the number of 7 - th grade keyboard players divided by the total number of 7 - th grade students. So $P=\frac{11}{40}$. Since 11 and 40 have no common factors other than 1, it is already in simplest form.

Answer:

$\frac{11}{40}$