The average height of a certain number of persons in a group is 155.5 cm. Later on 4 persons of height 154.6 cm, 158.4 cm, 152.2 cm and 153.8 cm leave the group. As a result the average height of the remaining persons increases by 0.15 cm. What was the number of persons initially in the group?
Show answer & explanation
Correct answer: D
Explanation
The correct answer is option 4 i.e. 24
Let the number of person be x then,
Average = Sum of all observations/Total number of observations
According to question,
155.5x - (154.6 + 158.4 + 152.2 + 153.8)}] = (x - 4) × 155.65
⇒ 155.5x - 619 = 155.65x - 622.6
⇒ 0.15x = -619 + 622.6 = 3.6
⇒ x = 3.6/0.15 = 24