Question

If a, b, c and d are proportional, then `(a + b)/(a − b)` is equal to ______.

Options

• `c/d`

• `(c - d)/(c + d)`

• `d/c`

• `(c + d)/(c - d)`

Answer 1

If a, b, c and d are proportional, then `(a + b)/(a − b)` is equal to `underlinebb((c + d)/(c - d))`.

Explanation:

Since a : b = c : d, the componendo-dividendo property gives `(a + b)/(a - b) = (c + d)/(c - d)`. The other options invert or alter this relation.