Consider the numbers a, b, c and d with values 54, 71, 75 and 99 respectively. Find the number which, when subtracted from each of them, makes a/b equal to c/d.
A5
B2
C3 ✓ Correct
D4
Correct answer: (C) 3
Explanation
The number to subtract is 3.
Require (54-x)/(71-x) = (75-x)/(99-x).
Cross-multiplying: (54-x)(99-x) = (75-x)(71-x).
Expanding gives 5346 - 153x = 5325 - 146x.
21 = 7x, so x = 3.
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