On a test consisting of 250 questions, Jassi answered 40% of the first 125 questions correctly. What percent of the other 125 questions does she need to answer correctly for her grade on the entire exam to be 60%?

### Concept & Strategy This is a weighted average problem. Because the test is split into two exactly equal halves (125 questions and 125 questions), the overall percentage is simply the arithmetic mean of the percentages of the two halves. $$\text{Overall } \% = \frac{\% \text{ of Part 1} + \% \text{ of Part 2}}{2}$$ ### Step-by-Step Solution * **Total Target:** The test has 250 questions. Jassi wants a 60% overall grade. $$\text{Target correct questions} = 60\% \text{ of } 250$$ $$\text{Target} = 0.6 \times 250 = 150 \text{ questions}$$ * **First Half Performance:** She answered 40% of the first 125 questions correctly. $$\text{Questions correct so far} = 40\% \text{ of } 125$$ $$\text{Correct} = 0.4 \times 125 = 50 \text{ questions}$$ * **Required Second Half Performance:** $$\text{Questions still needed} = 150 - 50 = 100 \text{ questions}$$ * **Calculate Required Percentage:** She needs 100 correct out of the remaining 125 questions. $$\text{Required } \% = \left(\frac{100}{125}\right) \times 100$$ $$\text{Required } \% = \left(\frac{4}{5}\right) \times 100 = 4 \times 20 = 80\%$$ ### Exam Strategy & Shortcut Bypass the total question counts entirely since the two parts are equal in size. Let the required percentage for the second half be $x\%$. $$\frac{40\% + x\%}{2} = 60\%$$ $$40 + x = 120$$ $$x = 80$$ This solves the problem mentally in under 5 seconds. ### Common Pitfall Students often get confused by the different bases and try to subtract percentages directly (e.g., $60\% - 40\% = 20\%$), failing to realize that a 60% overall requirement on double the volume requires significantly higher performance on the remaining half to pull the average up. ### Final Answer **Therefore, the correct answer is 80.**