If the average of the 3 digit numbers 335, 2x5, x35, 63x and 406 is 411, then what will be the average of x - 1, x - 3, x + 3 and x + 5 ?
If the average of the 3 digit numbers 335, 2x5, x35, 63x and 406 is 411, then what will be the average of x - 1, x - 3, x + 3 and x + 5 ? Correct Answer 5
Shortcut TrickSolve it by unit digit.
Unit digit of average is 1. The unit digit of the sum = 1 × 5 = 5
5 + 5 + 5 + x + 6 = 5
⇒ Unit digit of 21 + x = 5
⇒ 1 + x = 5
⇒ x = 4
Then,
Total sum of x - 1, x - 3, x + 3 and x + 5 = (4 - 1) + (4 - 3) + (4 + 3) + (4 + 5) = 3 + 1 + 7 + 9 = 20
∴ Average of x - 1, x - 3, x + 3 and x + 5 = 20/4 = 5
Traditional method:
Given:
Average of 335, 2x5, x35, 63x and 406 = 411
Formula:
Average = (Sum of terms)/(Number of terms)
Calculation:
Total of 335, 2x5, x35, 63x and 406 numbers = 411 × 5 = 2055
⇒ 335 + 2x5 + x35 + 63x + 406 = 2055
⇒ 300 + 30 + 5 + 200 + 10x + 5 + 100x + 30 + 5 + 600 + 30 + x + 400 + 0 + 6 = 2055
⇒ 1611 + 111x = 2055
⇒ x = 4
Then,
Total sum of x - 1, x - 3, x + 3 and x + 5 = (4 - 1) + (4 - 3) + (4 + 3) + (4 + 5) = 3 + 1 + 7 + 9 = 20
∴ Average of x - 1, x - 3, x + 3 and x + 5 = 20/4 = 5