1 Answers
Option 1 : 40.76
Given:
Batch A consists of 44 students and batch B consists of 56 student.
The average weight of batch A is 43 kg and that of batch B is 39 kg.
Formula used:
Combined average of 2 groups = (ma + nb)/(m + n)
Here,
m = numbers of members in group 1
n = numbers of members in group 2
a = average of group 1
b = average of group 2
Calculation:
Let the average of whole class be x.
x = (ma + nb)/(m + n)
⇒ x = (44 × 43 + 56 × 39/(44 + 56)
⇒ x = (1892 + 2184)/100
⇒ x = 4076/100
⇒ x = 40.76
∴ The average weight of whole class is 40.76 kg.
Alternate Method
Let the average weight of the whole class be 40 kg.
the average weight of batch A is exceeded by (43 - 40) = 3 kg
The total weight of batch A is exceeded by (44 × 3) = 132 kg
the average weight of batch B is inferior by (40 - 39) = 1 kg
The total weight of batch B is inferior by (56 × 1) = 56 kg
The total weight of the whole class is exceeded by (132 - 56) = 76 kg
The average of the whole class is exceeded by 76/100 = 0.76 kg
Required average = 40 + 0.76
⇒ Average = 40.76
∴ The average weight of the whole class is 40.76 kg.