Multiple choice

The average weight of $20$ students was calculated $70$ kg. It was later discovered that one weight was misread as $70$ instead of $90$, the correct average in kg is

  1. $80$
  2. $72$
  3. $75$
  4. $71$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The initial sum of weights was 20 * 70 = 1400. The error was subtracting 70 instead of 90, so the difference is +20. The corrected sum is 1420. The new average is 1420 / 20 = 71.

AI explanation

The total weight of the 20 students was initially calculated as 20 times 70, which equals 1400 kg. The actual total weight should be higher because one student's weight was misread as 70 instead of 90, meaning the total weight must increase by 20 kg to become 1420 kg. The correct average is found by dividing this new total by 20. The correct average is 71 kg.

Keep practicing — related questions