50 संख्याओ का औसत 30 है । बाद में ज्ञात हुआ की दो मानो को 28 एव 31 के स्थान पर 82 एव 13 गलती से अंकीत किया गया । सही औसत ज्ञात करे ?

Options

A. 36.12
B. 30.66
C. 29.28
D. 38.21

Answer

C

Explanation

According to the question
The mean of 50 no . Is =30
Sum of 50 no is =50x30=1500
later it was discovered that two entries were wrongly entered as 82 and 13 instead of 28 and 31.
`therefore` Difference =(82+13)-(28+31)
=95-59=36 (Extra)
`therefore` Actual sum of 50 numbers is = 1500-36=1464
`therefore` Actual avg. =`1464/50=29.28`
Alternate
Sum of wrongly entered numbers =82+13=95
sum of correct numbers =28+31=59
Required average `=30+(59-95)/50 =30-0.72 `
=29.28