BTGModeratorVI wrote: ↑

Mon Jul 13, 2020 8:06 am

A total of 22 men and 26 women were at a party, and the average (arithmetic mean) age of all of the adults at the party was exactly 35 years. If the average age of the men was exactly 38 years, which of the following was closest to the average age, in years, of the women?

(A) 31
(B) 31.5
(C) 32
(D) 32.5
(E) 33

Answer: D
Source: Official Guide

Weighted average of groups combined = (group A proportion)(group A average) + (group B proportion)(group B average) + (group C proportion)(group C average) + ...

There are 48 people in total.
So, 22/48 = the proportion of women
And 26/48 = the proportion of men

Let x = average age of the women

So, plugging the information into the formula, we get: (22/48)(38) + (26/48)(x) = 35
Simplify: (11/24)(38) + (13/24)(x) = 35
Multiply both sides by 24 to get: (11)(38) + 13x = (35)(24)
Simplify: 418 + 13x = 840
Rearrange: 13x = 422
Solve: x = 422/13 ≈ 32.5

Answer: D

Cheers,
Brent

BTGModeratorVI wrote: ↑

Mon Jul 13, 2020 8:06 am

A total of 22 men and 26 women were at a party, and the average (arithmetic mean) age of all of the adults at the party was exactly 35 years. If the average age of the men was exactly 38 years, which of the following was closest to the average age, in years, of the women?

(A) 31
(B) 31.5
(C) 32
(D) 32.5
(E) 33

Answer: D
Source: Official Guide

Solution:

1) Since there are 48 people (22 men and 26 women) and the average age of all of them is 35, the total ages of all the people at the party is 48(35).

2) Since there are 22 men and their average age is 38, the sum of all the men's ages is 22(38).

3) There are 26 women; letting their average age be x, the sum of all the women's ages is 26x.

Since the sum of the ages of all 48 people must be equal to the sum of the ages of the 22 men plus the sum of the ages of the 26 women, we have

48(35) = 22(38) + 26x

1680 = 836 + 26x

26x = 844

x = 844/26

x = 32 12/26 ≈ 32.5

Answer: D