Let's solve each geometric sequence one by one by first finding the common ratio $r$ and then using it to find the missing terms.

1. $3, 12, 48, \_, \_$

• Common ratio $r = \frac{12}{3} = 4$
• Next terms:
  • $48 \times 4 = 192$
  • $192 \times 4 = 768$

Sequence: $3, 12, 48, 192, 768$

2. $\_, \_, 32, 64, 128$

• Common ratio $r = \frac{64}{32} = 2$
• Previous terms:
  • $32 \div 2 = 16$
  • $16 \div 2 = 8$

Sequence: $8, 16, 32, 64, 128$

3. $120, 60, 30, \_, \_$

• Common ratio $r = \frac{60}{120} = \frac{1}{2}$
• Next terms:
  • $30 \times \frac{1}{2} = 15$
  • $15 \times \frac{1}{2} = 7.5$

Sequence: $120, 60, 30, 15, 7.5$

4. $5, \_, 20, 40, \_$

• Common ratio ( r = \frac{20}{5}