Question

last year at a certain high school, there were 60 ninth graders on the honor roll and 120 tenth graders on the honor roll. this year, the number of ninth graders on the honor roll decreased by 15% and the number of tenth graders on the honor roll decreased by 10%. by what percentage did the total number of students on the honor roll decrease? round your answer to the nearest tenth (if necessary).

Explanation:

Step1: Calculate new 9th grader count

$60 - (60 \times 0.15) = 60 - 9 = 51$

Step2: Calculate new 10th grader count

$120 - (120 \times 0.10) = 120 - 12 = 108$

Step3: Find original total honor roll

$60 + 120 = 180$

Step4: Find new total honor roll

$51 + 108 = 159$

Step5: Calculate total decrease amount

$180 - 159 = 21$

Step6: Compute percentage decrease

$\frac{21}{180} \times 100 \approx 11.7\%$

Answer:

11.7%