Question

answer following question

Answer 1

Let the percentage of   $\ce{^{10}_{5}X}$  be A %. Then the percentage of $\ce{^{11}_{5}X}$ be (100−A)%

$\therefore [10 \times \frac{A}{100}]+[11 \times \frac{100-A}{100}]= 10.8\\\implies 1100-A = 1080\\\implies A = 20$

So,

percentage of  isotope $\ce{^{10}_{5}X}$ = 20%

percentage of  isotope $\ce{^{11}_{5}X}$ = 80%

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