Question : The average of 20 numbers is 30 and that of the other 30 numbers is 50. What is the average of all the numbers?
Option 1: 42
Option 2: 47
Option 3: 44
Option 4: 45
Correct Answer: 42
Solution :
The sum of the 20 numbers = 20 × 30 = 600
The sum of the other 30 numbers = 30 × 50 = 1500
The total sum of both sets of numbers = 600 + 1500 = 2100
Total numbers = 20 + 30 = 50
$\therefore \text{Average}=\frac{\text{Sum of all numbers in both of the set of numbers}}{{\text{Total numbers}}}=\frac{2100}{50} = 42$
Hence, the correct answer is 42.
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