From the pie chart, 75% of pupils need glasses.<br>
75% corresponds to 27 pupils.<br><br>
1% = 27 &divide; 75 = 0.36 pupils.<br>
100% = 0.36 &times; 100 = 36 pupils.<br><br>
Check: 75% of 36 = \( \frac{75}{100} \) &times; 36 = 27. &check;<br><br>
Final Answer: 36