Bunuel
At a church prayer, (3/5)th of the members were males and (3/5)th of the male members attended the prayer. If (7/10)th of the female members attended the prayer, what fraction of the members at the prayer who did not attend the prayer are males?
(A) 1/4
(B) 3/7
(C) 2/3
(D) 9/10
(E) 6/19
Attachment:
prayermatrix.jpg [ 28.71 KiB | Viewed 4577 times ]
This language is misleading. We have:
A church prayer and
THE prayerThe first is a large category. The second is a small category and a subset of the first.
The categories are not similar. Time to rewrite:
Men and women are members of and in a CHURCH (= "
A church prayer")
Some men and women ATTEND a PRAYER in a separate room (= "
THE prayer")
We are interested in the group who goes to the separate room.
A double matrix is quick. Assign values.
The numbers in the matrix in the diagram were entered in the sequence below.
Use LCM of 5 and 10. Let total church members =
50• Number of male vs. number of female
CHURCH members (who may or may not attend a prayer)
Male, \(\frac{3}{5}\) of all members: \(\frac{3}{5}*50\) =
30Female, must be \(\frac{2}{5}\) of all: \(\frac{2}{5}*50\) =
20• Number of men and women in the church who DID and DID NOT attend a prayer
Females: \(\frac{7}{10}\) of all female members (20) DID attend a prayer: \((\frac{7}{10}*20)=14\)
Females who DID attend:
14Females who DID NOT attend: (20 - 14) =
6Males: \(\frac{3}{5}\) of all male members (30) attended a prayer: \((\frac{3}{5}*30)=18\)
Males who DID attend =
18Males who DID NOT attend: (30 - 18) =
12• TOTALS - who DID and DID NOT attend a prayer
Total WHO DID attend a prayer = (18 + 14) =
32Total who DID NOT attend a prayer: (50 - 32) =
18• What fraction of the members at the
prayer CHURCH, who did not attend
the A prayer, are males?
Total who DID NOT attend: 18
Number of that group who were male: 12
Fraction = \(\frac{12}{18}=\frac{2}{3}\)
Answer C