Question

If 12g of a radioactive substance are present initially and 8yr later only 6g remain, how much if the substance will be present after 13 years?

Answer 1

The weight of substance remaining after 13 years is 2.25 g.

Given:

Present weight of substance = 12 g

After 8 years weight remains = 6 gm

Now, weight loss in 8 year will be,

12-6=6 gm

So, weight loss in 1 year will be,

$\dfrac{6}{8} =\dfrac{3}{4}$

Total weight loss in 13 year will be,

$\dfrac{3}{4}\times13=9.75$

The weight of substance remaining after 13 years will be,

$12- 9.75 = 2.25 \;\rm g$

Therefore, the weight of substance remaining after 13 years is 2.25 g.

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