$\"\"$

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The decay function is $\"\"$ .

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(a).

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After an year the mass of tritium-3 is decayed to $\"\"$ .

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Find the mass of the function after an year.

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Substitute $\"\"$ in the equation $\"\"$ .

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$\"\"$

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Substitute $\"\"$ in the equation $\"\"$ .

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$\"\"$ .

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Let the half life be $\"\"$ then $\"\"$ .

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$\"\"$

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Substitute $\"\"$ in the above equation

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$\"\"$

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Apply logarithm on each side.

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$\"\"$

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Half life time is $\"\"$ years.

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$\"\"$

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(b)

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The decay function is $\"\"$ .

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Find the value of $\"\"$ .

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$\"\"$

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$\"\"$

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$\"\"$ .

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Find time to decay $\"\"$ % of its original amount.

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$\"\"$

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$\"\"$

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Substitute $\"\"$ in the above equation.

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$\"\"$

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Time taken to decay to $\"\"$ % of its original amount is $\"\"$ years.

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$\"\"$

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(a) Half life time is $\"\"$ years.

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(b) Time taken to decay to $\"\"$ % of its original amount is $\"\"$ years.