In a Maths excellence competition, there are 47 male and

Question

In a Maths excellence competition, there are 47 male and female students. Among the female students:
+ 1st female student knows 16 male students.
+ 2nd female student knows 17 male students.
+ 3rd female student knows 18 male students.
...................................................................
+Last female student knows all of the male students.

How many male students are there in the competition?

A. 30
B. 31
C. 32
D .33
E. 34

devilmirror · Answer

1st female student knows 16 male: Total 17 students
2nd female student knows 17 male: Total 19 students
3rd female student knows 18 male: Total 21 students

Sequence: 17, 19, 21, ... And assuming f = female student
OR
17 + 2(1-0), 17 + 2(2-1), 17 + 2(3-1), ..., 17 + 2(f-1)

47 = 17 + 2(f-1)
30 = 2(f-1)
f = 16

Male students = 47 - 16 = 31

B. is the answer.

trivikram · Answer

+ 1st female student knows 16 male students. 
+ 2nd female student knows 17 male students. 
+ 3rd female student knows 18 male students. 
................................................................... 
+Last female student knows all of the male students


So nth female student knows (n+15) male students

So 2n + 15 =47

n = 16

Number of male students = 31

amorpheus · Answer

f(1) = 16
f(2) = 17
f(3) = 18
...
f(15) = 30
f(16) = 31----Answer
f(30)= 45

bz9 · Answer

With each female we increase by two. 1 female 1 male. 

With 3 females and 18 males we have 21 and 47 - 21 = 26 or 26 more place/students. 26/2 = 13 males. 

18 + 13 = 31

In a Maths excellence competition, there are 47 male and

Prep Toolkit

Top 5 GMAT Debrief Videos

615 to 715 in 15 Days (Ria's Strategies)

More than Quant/Verbal Abilities: Speed vs. Accuracy

745 with Only Self-Prep and GMAT Club

From 555 to 765: 210-point Improvement

Perfect 805 Score Debrief by Julia

My Rewards