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  4. Mean of 100 items is 49. It was discovered that three items which should have been 60, 70, 80 were wrongly read as 40, 20,50 respectively. The correct mean is

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Q. Mean of $100$ items is $49$. It was discovered that three items which should have been $60, 70, 80$ were wrongly read as $40, 20,50$ respectively. The correct mean is

Statistics

Solution:

Sum of $100$ items $= 49 \times 100 = 4900$
Sum of items added $= 60 + 70 +80 = 210$
Sum of items replaced $= 40 +20 + 50 =110$
New sum $ = 4900+ 210 -110 = 5000$
$\therefore $ Correct mean $= \frac{5000}{100} = 50$