The element is remaining after 18 minutes with the rate of decaying of 26.8 % is 2.99 grams.
The amount of something is expressed as if it is a part of the total which is a hundred. The ratio can be expressed as a fraction of 100. The word percent means per 100. It is represented by the symbol ‘%’.
An element with a mass of 820 grams decays by 26. 8% per minute.
Then the mass remaining after one minute will be
Remaining = 100 - 26.8
Remaining = 73.2 %
The element is remaining after 18 minutes will be
Mass = 820 × (0.732)¹⁸
Mass = 820 × 0.00364
Mass = 2.985
Mass ≈ 2.99
The element is remaining after 18 minutes is 2.99 grams.
More about the percentage link is given below.
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