1st Year entrants = 1000
2nd Year entrants = 1000 * 1.1 = 1100
3rd Year entrants = 1100 * 1.1 = 1210
4th Year entrants = 1210 * 1.1 = 1331
The total population at the end of the 4th year in a school containing 4 or more grades is 1000 + 1100 +1210 + 1331 = 4641.
The total population at the end of the 4th year in a school containing 3 grades is 1100 + 1210 + 1331 = 3641.
The total population at the end of the 4th year in a school containing 2 grades is 1210 + 1331 = 2541.
The total population at the end of the 4th year in a school containing only 1 grade is 1331.