On the second day he wrote twice the amount as the first day, which was 25 pages so 2*25 = <<2*25=50>>50 pages
On the third day he wrote twice the amount as he did on the second day, which was 50 pages so 2*50 = <<2*50=100>>100 pages
The first day he wrote 25, then 50, then 100 and 10 on the fourth day for a total of 25+50+100+10 = <<25+50+100+10=185>>185
He needs to write 500 pages and has written 185 which means he has 500-185 = <<500-185=315>>315 more pages to write
#### 315