Does anyone know the answer to this chemistry problem? Can you please help? ?

Question

An imaginary element Xq consists of two isotopes having masses of 100.0 amu and 102.0 amu. A sample of Xq was found to contain 20.0% of the 100Xq isotope and 80.0% of the 102Xq isotope. Calculate the atomic weight of Xq.

A). 100.2 amu

B). 100.4 amu

C). 101.0 amu

D). 101.6 amu

E). 202.0 amu

Answer 1

the atomic weight is the weighted average of all the isotopes of an element. Foe the fuctitious element Xq , it has but two isotopes so its atomic weight will be the weighted average of the two..If isotope weigghing 102 is 80% of the composite weight then 0.8 X 102 = 81.6

The other isotope comprises ( obviously ) the otjher 20% of the composite average..so 0.2 ( 100) = 20  adding the two together

81.6 + 20 = 101.6

Answer 2

I think the answer is D.

x=100.0 amu

y=102.0 amu

.2x + .8y=

.2(100) + .2(102.0)=

20 + 81.6 = 101.6

D). 101.6