11. Among the two hundred natural numbers from 1 to 200, list in ascending order those that are neither multiples of 3 nor multiples of 5. The 100th number in this sequence is
【Answer】187
【Analysis】Key points: Period, Number Theory
The least common multiple of 3 and 5 is 15, in the numbers from 1 to 15, the numbers that are neither multiples of 3 nor multiples of 5 are: $1, 2, 4, 7, 8, 11, 13, 14$, there are 8 such numbers, so the period is 8, $100 \div 8=12 \cdots 4$, therefore, the 100th number is $12 \times 15+7=187$