1. **Stating the problem:** We are given a sequence where the number of small triangles for Figure 1 is 4, and for Figure 2 is 9. We need to find the number of small triangles for Figures 3 to 8. 2. **Observing the pattern:** The numbers 4 and 9 correspond to $2^2$ and $3^2$ respectively. 3. **Hypothesis:** The number of small triangles for Figure $n$ seems to be $ (n+1)^2 $. 4. **Testing the hypothesis:** - For Figure 1: $ (1+1)^2 = 2^2 = 4 $ (matches given data) - For Figure 2: $ (2+1)^2 = 3^2 = 9 $ (matches given data) 5. **Calculating for Figures 3 to 8:** - Figure 3: $ (3+1)^2 = 4^2 = 16 $ - Figure 4: $ (4+1)^2 = 5^2 = 25 $ - Figure 5: $ (5+1)^2 = 6^2 = 36 $ - Figure 6: $ (6+1)^2 = 7^2 = 49 $ - Figure 7: $ (7+1)^2 = 8^2 = 64 $ - Figure 8: $ (8+1)^2 = 9^2 = 81 $ 6. **Final answer:** The number of small triangles for Figures 3 to 8 are 16, 25, 36, 49, 64, and 81 respectively.