Jacob can write twice as fast as Nathan. Nathan wrote 25 letters in one hour. How many letters can the two write in 10 hours together?
Since Nathan writes 25 letters in an hour, Jacob writes 25*2 = <<25*2=50>>50 letters in an hour.
Together, they write 50+25 = <<50+25=75>>75 letters in an hour,
In 10 hours, they'll write a total of 75*10 = <<10*75=750>>750 letters
#### 750