Question
The average of 7 numbers is 28. The average of first
three of them is 23 and the last three of them is 42. Then the fourth number is:Solution
We know that, Average = Sum of all quantities/number of quantities Average of 7 numbers = 28 ∴ Sum of all numbers = 28 × 7 = 196 Average of first 3 numbers is 23. Sum of first 3 numbers = 3 × 23 = 69 Average of last 3 numbers os 42. Sum of last 3 numbers = 3 × 42 = 126 4th number = 196 – 69 – 126 = 1
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