Answer:
10,542,719
Explanation:
The circle chart shows you that an estimated 49% of Australia's population has type O blood. Then the number expected to have type O blood is ...
0.49 × 21,515,754 ≈ 10,542,719
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You can choose the correct answer by recognizing that 49% is very slightly less than 1/2, so the number with type O blood will be very slightly less than half of 21 million -- about 10.5 million.