Question 30
The average marks of 40 students in an English exam is 72. Later it is found that three marks 64, 62 and 84 were wrongly entered as 68, 65 and 73. The average after mistakes were rectified is
Solution
average marks of 40 students in an English exam is 72
total marks = $$ 72 \times 40 = 2880 $$
three marks 64, 62 and 84 were wrongly entered as 68, 65 and 73
average after mistakes were rectified
$$ 2880 - (68 + 65 + 73) +(64 + 62 + 84 ) $$
$$ 2880 - 206 + 210 = 2884 $$
Required average = $$ \frac {2884}{40} = 72.1$$
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