Math, asked by VINEET7521, 1 year ago

In a class of 45 students, boys and girls are in the ratio of 5 : 4 respectively. The average marks obtained in mathematics out of 100 were 76 and that of girls were 78. What is the average marks of boys and girls together in mathematics (rounded-off to two decimal points)?

Answers

Answered by amitnrw
11

Answer:

76.89

Step-by-step explanation:

Let say boys and girls are 5x & 4x respectively

5x + 4x = 9x = 45

x = 5

Boys = 5*5 = 25

Grils = 4*5 = 20

Assuming 76 is average marks of boys as its not mentioned in question .

Total Marks of Boys = 25*76 = 1920

Total Mark of Girls = 20 * 78 = 1560

Total Marks of Boys + Girls  = 1900 + 1560 =  3460

Average marks of boys + girls = 3460/45 = 76.89

average marks of boys and girls together in mathematics = 76.89

Answered by Anonymous
13

Answer:

76.89


Step-by-step explanation:


Ratio of boy : girls = 5 : 4 .

Let the number of boys be 5 x .

Let the number of girls be 4 x .


Given in the question :

Total number of students = 45 .

This implies that the sum of boys and girls = 45.

⇒ 5 x + 4 x = 45

⇒ 9 x = 45

⇒ x = 45/9

⇒ x = 5.


Hence the number of boys = 5 × 5 = 25 .

The number of girls = 4 × 5 = 20 .


The average marks of boys = 76 .

The average of marks of girls = 78 .


Average = sum of all observations / number of observations .


Number of girls = 20 .

Average = 78 .


⇒ 78 = sum of all marks of girls / 20

⇒ sum of marks of girls = 78 × 20

⇒ sum of marks of girls = 1560 .


Similarly :

Sum of marks of boys / 25 = 76

⇒ sum of marks of boys = 76 × 25

⇒ sum of marks of boys = 1900 .


Total marks = 1900 + 1560

                    = 3460 .


Average marks all together = sum / number of boys/girls .


⇒ Average = 3460 / 45


                       45 )3460( 76.888

                              315

                             --------

                                  310

                                  270

                                  -----------

                                      400

                                       360

                                     -------------

                                            400

                                             360

                                          ---------------

                                                  400

                                                   360

                                                     --------

                                                       40

⇒ Average = 76.89


76.89 [ in two decimal places ]

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