Question

shandra recorded the grade - level and instrument of everyone in the middle school school of rock below.
seventh grade students

instrument	# of students
bass	11
drums	11
keyboard	13

eighth grade students

instrument	# of students
bass	9
drums	15
keyboard	2

based on these results, express the probability that a seventh grader chosen at random will play the bass as a percent to the nearest whole number.

Explanation:

Step1: Calculate total number of seventh - grade students

Add the number of students for each instrument in the seventh - grade table.
$$9 + 11+11 + 13=44$$

Step2: Calculate the probability of a seventh - grader playing bass

The number of seventh - graders playing bass is \(11\). Use the probability formula \(P=\frac{\text{Number of favorable outcomes}}{\text{Total number of outcomes}}\).
The probability as a fraction is \(\frac{11}{44}\). To convert it to a percentage, use the formula \(P(\%)=\frac{11}{44}\times100\).
$$\frac{11}{44}\times100=\frac{100}{4}=25$$

Answer:

\(25\%\)