Among the numbers from 1 to 20, count how many of their Roman numerals contain the symbol V at least once.
How many such numbers are there?

The character V appears in: 4(IV), 5(V), 6(VI), 7(VII), 8(VIII) — 5 numbers; and 14(XIV), 15(XV), 16(XVI), 17(XVII), 18(XVIII) — 5 numbers. Total = 5 + 5 = 10 numbers. (9=IX and 19=XIX use only I and X; 4=IV and 14=XIV do contain the letter V.)