Step 1: Determine the Number of Boys and Girls
We are given that the total number of students is 400. Let:
- The number of girls be \( x \)
- The number of boys be \( 3x \)
The total number of students is:
\[ x + 3x = 400 \]
Solving for \( x \):
\[ 4x = 400 \Rightarrow x = 100 \]
Thus:
- Number of girls = 100
- Number of boys = 3 × 100 = 300
Step 2: Calculate the Number of Students Who Walk to School
- 70% of the boys walk to school:
- 60% of the girls walk to school:
Step 3: Find the Total Number of Students Who Walk to School
\[ 210 + 60 = 270 \]
Step 4: Calculate the Percentage of Students Who Walk to School
\[ \frac{270}{400} \times 100 = 67.5\% \]
Final Conclusion:
Thus, the percentage of students who walk to school is 67.5%.