Step-by-step Solution:

Let's assume the total number of students is 100 for easy calculation.
Step 1: Students Who Passed the Half-Yearly Exam
60% of students passed the half-yearly exam.
So, the number of students who passed the half-yearly exam = \[ \frac{60}{100} \times 100 = 60 \] 40% failed the half-yearly exam.
So, the number of students who failed the half-yearly exam = \[ \frac{40}{100} \times 100 = 40 \] Step 2: Students Who Passed the Annual Exam
70% of students who passed the half-yearly exam passed the annual exam: \[ \frac{70}{100} \times 60 = 42 \] 80% of students who failed the half-yearly exam passed the annual exam: \[ \frac{80}{100} \times 40 = 32 \] Step 3: Total Students Who Passed the Annual Exam \[ 42 + 32 = 74 \] Step 4: Percentage of Students Who Passed the Annual Exam
Since the total number of students was 100, the percentage of students who passed the annual exam is: \[ \frac{74}{100} \times 100 = 74\% \] Final Answer \( 74\% \)