2520. you just have to find the least common multiple of 1 through 10. it must be even, end in 0, and divisible by all other integers. the lcm of 1 through 6 is 60 (which is pretty easy to find). the lcm of 1 through 7 is 420 (60x7). the lcm of 1 through 8 is 840 because 420/8=52.5, so you multiply by 2 to get an integer. by this same logic, you get 2520 for one through 9 and since it is a multiple of 10 you are done.