Explanation
Given:
A set of consecutive positive integers beginning with 1 is written on the blackboard. A student came along and erased one number. The average of the remaining numbers is 35177.
Formula Used:
average = sum of observations/number of observation
average of n consecutive number = 2n(n+1)n = 2(n+1)
Calculation:
Since the average of the remaining numbers is 35177
To get an average greater than 35, the value of n must be near 69.
Let initially number of terms be 69 and the number which was erased be 'x'
⇒(69×35−x)/68=602/17
⇒2415−x=2408
⇒x=7
∴ The number erased was 7
