Element X decays radioactively with a half life of 9 minutes. If there are 890 grams of Element X, how long, to the nearest tenth of a minute, would it take the element to decay to 238 grams?

13.18651685

13.9

Explain:

890-238=652
652/890=0.7325842697 (Find out the percentage)

We know that 1 gram of Element X will be fully decayed in 18 minutes and half of it in 9 minutes.

0.7325842697x18=13.18651685

As you see 18/13.18651685 will equal to 18 (not exactly since it is rounded)

And of course we need to round it to nearest tenth. So the answer would be 13.9!

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