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?
Let the number of persons initially be $$x$$
=> Total height initially = $$155.5x$$ cm
Height of the 4 people that left = $$154.6+158.4+152.2+153.8=619$$ cm
According to ques, new average :
=> $$\frac{155.5x-619}{x-4}=155.65$$
=> $$155.5x-619=155.65x-622.6$$
=> $$0.15x=3.6$$
=> $$x=\frac{360}{15}=24$$
$$\therefore$$ There were 24 persons initially.
=> Ans - (D)
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