Refer to the radioisotope colbalt-60, which has a half life of 5.3 years. An initial sample of colbalt-60 has an activity of 12,400cpm. How much time has passed if the activity of the sample has dropped to 775cpm

21.2 years

Explanation:

If half life is 5.3 years, that means activity will be 50% every 5.3 years.

12,400 x 50% = 6,200

6,200 x 50% = 3,100

3,100 x 50% = 1,550

1,550 x 50% = 775

4 half lives, so 4 half lives x 5.3 years/half life = 21.2 years

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explanation:

under a microscope, cancer cells may look very different from normal cells. they often have different sizes and some may be larger than normal while others are smaller. cancer cells are often abnormally shaped and the control centre of the cell (the nucleus) may have an abnormal appearance.

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