Answer:
16000 = 2 × 2 × 2 × 2 × 2 × 2 × 2 × 5 × 5 × 5
16000 = 2³ × 2³ × 2 × 5³
if we mutiply 2³ × 2³ × 2 × 5³ by 2 × 2 , it becomes perfect cube , like it becomes 2³ × 2³ × 2³ × 5
therefore we have to multiply 2×2 = 4 with 16000 to make it perfect cube