a class of 35 students has an average height of 180 cm . 7 students whose average height is 120 cm , left the class and 7 others whose average height is 140 cm , joined . calculate the new average height of the students of the class ( in cm ) is ?  Choose the correct choice from the following options:  A) 204.6 cm  B) 404.6 cm  C) 224.6 cm  D) 205.6 cm  E) 256.6 cm

Rationale: total height = 180 * 35 = 6300 cm . total height of those who left = 120 * 7 = 840 total height of those who joined = 140 * 7 = 980 new average = [ 6300 - 120 + 980 ] / 35 = 7160 / 35 cm . = 204.6 cm answer : a
Answer: A