1.

The average of 17 results is 60. If the average of first 9 results is 57 and that of the last 9 results is 65, then what will be the value of 9th result?1). 392). 783). 1174). 156

Answer»

Average of all 17 results is = 60

Sum of all 17 results = 60 × 17 = 1020

Average of first 9 results = 57

Sum of first 9 results = 57 × 9 = 513

Average of LAST 9 results = 65

Sum of last 9 results = 65 × 9 = 585

Both SUMS I.e. of first 9 and last 9 digits include the 9 result

So if we add both sums it will have the 9th result one extra time and we can subtract the actual sum from this ADDITION to GET the 9th result

So sum of first and last 9 results = 513 + 585 = 1098

∴ The 9th result will be = 1098 - 1020 = 78


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