Please can someone help with with this calculation for atomic mass

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    Said what I wanted to say above ...
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    (Original post by JackT2000)
    Said what I wanted to say above ...

    Relative atomic mass = ((isotope number X abundance)+(isotope number X abundance)) / 100

    The abundance is the percentage

    So, in your case:

    (63 X 69) + (65 X 31) / 100 = 63.62

    It is best to try to round your numbers to 3 significant figures, unless the question specifies otherwise, so in this case the answer would be 63.6. However, 63.62 would probably still give you full marks in the exam.
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