Given: In a class of 250 students, 40% are boys. The average height of the boys is 100 cm, and that of the girls is 80 cm. Concept used : Average = Sum of all observations/Number of observations Calculations : Total number of students in the class = 250 Number of boys in class(40%) = (40/100) × 250 = 100 Number of girls in class(60%) = (60/100) × 250 = 150 Average height of girls = 80 cm Sum of height of girls = 80 × 150 = 12000 cm Average height of boys = 100 cm Sum of height of boys = 100 × 100 = 10000 Total sum of height of all class = 12000 + 10000 = 22000 Average height of whole class = 22000/250 ⇒ 88 cm Difference of the average height of the girls and whole class = 88 - 80 ⇒ 8 cm ∴ The correct choice will be option 4.