Question

please help answer q-11 with method

Answer 1

Sum of marks of all students = 72 × 100 = 7200
Sum of marks of boys = 75 × 70 = 5250

Sum of marks of girls = 7200 - 5250 = 1950
Number of girls = 100 - 70 = 30
Mean mark of girls = 1950/30 = 65

Option (2)

Answer 2

Given that total number of students = 100.

Given that there are 70 boys in the class.

Number of girls = 100 - 70

                          = 30.


Given that Mean marks of 100 students in a class was 72.

= > 100 * 72

= > 7200.


Given that Mean of marks for boys was 75. The total number of boys = 70.

= > 70 * 75

= > 5250.


That means mean of marks of girls = 7200 - 5250

                                                            = 1950.



Therefore, the average marks of girls = Mean Marks of girls/Number of girls

                                                                = 1950/30

                                                                = 65.



Hope this helps!