Solution
Given : $$(x + y) = 13$$ and $$x^2 + y^2 = 89$$
Using $$(x + y)^2 = x^2 + y^2 + 2xy$$
=> $$(13)^2 = 89 + (2 \times xy)$$
=> $$2 xy = 169 - 89 = 80$$
=> $$xy = \frac{80}{2} = 40$$
=> Ans - (D)
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