The half-life of a radioactive isotope is the time it takes for a quantity of the isotope to be reduced to half its initial mass. Starting with 145 grams of a radioactive isotope, how much will be left after 4 half-lives? Use the calculator provided and round your answer to the nearest gram. grams $\times \quad 5$

Step 1 ：The half-life of a radioactive isotope is the time it takes for a quantity of the isotope to be reduced to half its initial mass. This means that after each half-life, the mass of the isotope is halved. Therefore, after 4 half-lives, the mass of the isotope will be halved 4 times.

Step 2 ：We can calculate this by starting with the initial mass and dividing by 2 for each half-life. The initial mass is 145 grams.

Step 3 ：First half-life: \(\frac{145}{2} = 72.5\) grams

Step 4 ：Second half-life: \(\frac{72.5}{2} = 36.25\) grams

Step 5 ：Third half-life: \(\frac{36.25}{2} = 18.125\) grams

Step 6 ：Fourth half-life: \(\frac{18.125}{2} = 9.0625\) grams

Step 7 ：Rounding to the nearest gram, we get 9 grams.

Step 8 ：Final Answer: After 4 half-lives, there will be approximately \(\boxed{9}\) grams of the radioactive isotope left.