#
Arathi took 3 examinations in a year. The

marks obtained by her in the second and third

examinations are more than 5 and 10 respectively

than in the first examination. If her average mark

is at least 80 find the minimum mark that she

should get in the first examination?

$Letthemarksobtainedinfirstexambe\text{'}x\text{'}\phantom{\rule{0ex}{0ex}}Marksobtainedinsecondexam=x+5\phantom{\rule{0ex}{0ex}}Marksobtainedinthirdexam=x+10\phantom{\rule{0ex}{0ex}}Averagemarks=\frac{sumofmarksobtained}{No.ofmarks}\phantom{\rule{0ex}{0ex}}\Rightarrow 80=\frac{x+x+5+x+10}{3}\phantom{\rule{0ex}{0ex}}\Rightarrow 80=\frac{3x+15}{3}\phantom{\rule{0ex}{0ex}}\Rightarrow 80=x+5\phantom{\rule{0ex}{0ex}}\Rightarrow 80-5=x\phantom{\rule{0ex}{0ex}}\Rightarrow x=75\phantom{\rule{0ex}{0ex}}Thusmarksobtainedinfirstexamis75\phantom{\rule{0ex}{0ex}}$

Regards

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