Exams › SSC CGL (Prelims) › Maths

If $a^2 - b^2 = 81$ and $a - b = 3$, find $a + b$.

1. 30
2. 27
3. 18
4. 15

Correct answer: 27

Solution

We use the identity $a^2-b^2=(a-b)(a+b)$. Given $a^2-b^2=81$ and $a-b=3$, we get $3(a+b)=81$, so $a+b=27$.

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