5. Among the natural numbers $1,2, \cdots, 50$, the numbers that leave a remainder of 1 when divided by 3 are $\qquad$ in number.
【Key Point】Divisibility
【Difficulty】Comprehension

【Answer】 17
【Analysis】Multiples of 3 are $50 \div 3=16 \cdots 2 . \quad 16+1=17$ (numbers).