Question
Expand: $\left(3 \mathrm{x}+\frac{1}{3 \mathrm{x}}\right)^2$
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Answer
$ \left(3 \mathrm{x}+\frac{1}{3 \mathrm{x}}\right)^2$
$=(3 \mathrm{x})^2+\left(\frac{1}{3 \mathrm{x}}\right)^2+2 \times 3 \mathrm{x} \times \frac{1}{3 \mathrm{x}}$
$ =9 \mathrm{x}^2+\frac{1}{9 \mathrm{x}^2}+2$
$=(3 \mathrm{x})^2+\left(\frac{1}{3 \mathrm{x}}\right)^2+2 \times 3 \mathrm{x} \times \frac{1}{3 \mathrm{x}}$
$ =9 \mathrm{x}^2+\frac{1}{9 \mathrm{x}^2}+2$
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(iii) C secured 51 marks out of 75 . $\quad$ (iv) D secured 87 marks out of 120 .
1. Which of the four friends had the best performance?
(a) A $\quad$(b) B $\quad$(c) C $\quad$(d) D
2. C got his test paper re-evaluated and his score increased by $12 \%$. His new score is :
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3. If the pass percentage in A's test was $40 \%$, how many percent more marks did he obtain than the passing marks ?
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4. If D obtained 45 marks more than the passing marks, then what was the pass percentage in his test?
(a) $34 \%$ $\quad$(b) $35 \%$ $\quad$(c) $38 \%$ $\quad$(d) $40 \%$
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