The average of 8 numbers is 18. If one of the numbers is excluded, the average becomes 20. Find the excluded number. 

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SSC CGL 2023 Tier-I Official Paper (Held On: 19 Jul 2023 Shift 4)
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  1. 6
  2. 10
  3. 8
  4. 4

Answer (Detailed Solution Below)

Option 4 : 4
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Detailed Solution

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Given : 

Average of 8 numbers is 18.

One of the numbers is excluded, the average becomes 20.

Formula Used : 

Average =  Sum of all observations/Number of observations

Calculation : 

Sum of 8 numbers = 18 × 8 = 144

Sum of 7 numbers = 20 × 7 = 140

Excluded number = 144 - 140 = 4

∴ The correct answer is 4.

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