Explanation:

As per the give table,
Total number of student in the college A$$={\displaystyle \frac{25\times 8000}{100}}=2000$$
Total number of student in the college B$$={\displaystyle \frac{35\times 10000}{100}}=3500$$
Total number of student in the college C$$={\displaystyle \frac{45\times 15000}{100}}=6750$$
Total number of student in the college D$$={\displaystyle \frac{28\times 9000}{100}}=2520$$
Total number of student in the college A$$={\displaystyle \frac{35\times 11000}{100}}=3850$$
Hence average number of students are studying in all the colleges$$={\displaystyle \frac{2000+3500+6750+2520+3850}{5}}=3724$$