按规律填数3,6,9,18,21()()903,6,9,18,21()()90.这个怎么填
问题描述:
按规律填数3,6,9,18,21()()90
3,6,9,18,21()()90.这个怎么填
答
规律:3×2=6 6+3=9 9×2=18 18+3=21 21×2=42 42+3=45 45×2=90 答案:(42) (45)