Arithmetichard · Past Paper
If a/b = 4/5 and b/c = 15/16, find the value of (c^2 - a^2) / (c^2 + a^2).
A1/7
B7/25
C3/4
DNone
✓ Correct Answer: B — 7/25
a/c = (a/b)*(b/c) = (4/5)*(15/16) = 3/4. Let a=3k, c=4k. Expression = (16k^2 - 9k^2)/(16k^2 + 9k^2) = 7/25.
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