Answer: The blue whale's weight is 150 times heavier than the narwhal's weight.
Step-by-step explanation:
Given: Weight of Blue whale = [tex]3\times10^5\text{ pounds}[/tex]
Weight of Narwhal = [tex]2\times10^3\text{ pounds}[/tex]
Number of times blue whale's weight  is heavier than the narwhal's weight = [tex]=\dfrac{\text{Weight of Blue whale}}{\text{Weight of Narwhal }}[/tex]
[tex]=\dfrac{3\times10^5}{2\times10^3}\\\\=1.5\times10^{5-3}\ \ \ [\dfrac{a^m}{a^n}=a^{m-n}]\\\\=1.5\times10^2\\\\=1.5\times100=150[/tex]
Hence, the blue whale's weight is 150 times heavier than the narwhal's weight.