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In the number 1.4ab5, a and b represent single positive digits. If x = 1.4ab5, what is the value of 10 - x?
(1) If x is rounded to the nearest hundredth, then 10 - x = 8.56.
(2) If x is rounded to the nearest thousandth, then 10 - x = 8.564.
In the original condition there are 2 variables (a, b) thus we need 2 equations to match the number of variables. C is likely the answer. Solving the problem using (1) &(2), a=3, b=6 thus the answer is C. Remember to apply common mistake types in such integer problems. When we apply 'When it's easily C, consider A, B.' from common mistake types 4(A), and consider (1), we have variables with unknown values. In case of (2), a = 3, b =6 , therefore it is unique, and therefore the answer is B.
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