If Jina reads 90 pages a day, it will take her more than 4 days to finish reading a
book. If she reads 80 pages a day, she will take less than 5 days. If the number of
days Jina takes to finish reading is the same as the number of pages she reads
every day, how many pages she must read every day?
So, if there are p pages, then
360 < p < 400
so, if she takes n days, at n pages/day, we have n^2 = p
19^2 = 361