# Question a920f

Jul 25, 2016

b) -> 8.75

#### Explanation:

Out of 44

$\frac{9}{44} \times 10 = 2.045 \overline{45} \leftarrow 2 \frac{1}{22}$

$\frac{15}{44} \times 9 = 3.0681 \overline{81} \leftarrow 3 \frac{3}{44}$

$\frac{20}{44} \times 8 = 3.63 \overline{63} \leftarrow 3 \frac{7}{11}$

The 'Expectation' (mean value) is $8 \frac{3}{4}$

Aug 23, 2016

Mean = $\frac{385}{44} = 8.75$ years

#### Explanation:

To find the mean of a set of date we use the following method:

Mean = ("sum of all the values")/("the number of values") = "total"/"number" or " M=T/N#

Remember, we can add numbers, we can add totals,
WE CANNOT ADD MEANS!

For the 44 boys in the class , we can find the sum of all their ages.

9 boys are all 10 years old, the sum of their ages is $9 \times 10 = 90$
15 boys are all 9 years old, the sum of their ages is $15 \times 9 = 135$
20 boys are all 8 years old:, the sum of their ages is $20 \times 8 = 160$

$90 + 135 + 160 = 385$

For the 44 boys, the sum of their ages is 385 years.

Mean = $\frac{385}{44} = 8.75$ years