Part A: The problem 49/0.07 can be rewritten as 4900/7 by multiplying numerator and denominator by 100. Then it is more clear that the correct answer is (49/7)×100 = 700.
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Part B: I've always had trouble reading Marco's mind, so I cannot tell you what mistake he made. I can tell you the decimal point in his result is in the wrong place.
