3. The mean of 9 observations is 50. Four of the 9 observations are 20, 21, 22, 23. The remaining five numbers are in the ratio [tex]$2:4:5:6:9$[/tex]. Find those numbers.



Answer :

To find the remaining five numbers given their ratio and the mean of the observations, follow these steps:

1. Calculate the total sum of all observations:
The mean of observations is given as 50, and there are 9 observations in total.

[tex]\[ \text{Total sum} = (\text{Mean}) \times (\text{Number of observations}) = 50 \times 9 = 450 \][/tex]

2. Calculate the sum of the given observations:
The four given observations are 20, 21, 22, and 23.

[tex]\[ \text{Sum of given observations} = 20 + 21 + 22 + 23 = 86 \][/tex]

3. Find the sum of the remaining observations:
Subtract the sum of the given observations from the total sum of all observations to find the sum of the remaining five observations.

[tex]\[ \text{Sum of remaining observations} = \text{Total sum} - \text{Sum of given observations} = 450 - 86 = 364 \][/tex]

4. Analyze the ratio of the remaining five numbers:
The ratio given for the remaining five numbers is [tex]\(2:4:5:6:9\)[/tex]. Let's denote these five numbers as [tex]\(2x, 4x, 5x, 6x,\)[/tex] and [tex]\(9x\)[/tex]. The total parts of the ratio are:

[tex]\[ 2 + 4 + 5 + 6 + 9 = 26 \][/tex]

This means each part of the ratio represents a fraction of the sum of the remaining observations.

5. Determine each remaining number based on the ratio:
Since the sum of the remaining observations is 364, we can find each number corresponding to its ratio part of the total sum. So,

[tex]\[ 2x = \frac{2}{26} \times 364 = \frac{2 \times 364}{26} = 28 \][/tex]

[tex]\[ 4x = \frac{4}{26} \times 364 = \frac{4 \times 364}{26} = 56 \][/tex]

[tex]\[ 5x = \frac{5}{26} \times 364 = \frac{5 \times 364}{26} = 70 \][/tex]

[tex]\[ 6x = \frac{6}{26} \times 364 = \frac{6 \times 364}{26} = 84 \][/tex]

[tex]\[ 9x = \frac{9}{26} \times 364 = \frac{9 \times 364}{26} = 126 \][/tex]

So, the remaining five numbers are [tex]\(28, 56, 70, 84,\)[/tex] and [tex]\(126\)[/tex].