R is the set of positive odd integers less than 50, and S is the set of squares of the integers in R. How many elements

This topic has expert replies
Moderator
Posts: 2505
Joined: Sun Oct 15, 2017 1:50 pm
Followed by:6 members
Source: GMAT Prep

R is the set of positive odd integers less than 50, and S is the set of squares of the integers in R. How many elements has the intersection of R and S contain?

A. One
B. Two
C. Four
D. Five
E. Seven

The OA is C
Source: — Problem Solving |

GMAT/MBA Expert

User avatar
GMAT Instructor
Posts: 16207
Joined: Mon Dec 08, 2008 6:26 pm
Location: Vancouver, BC
Thanked: 5254 times
Followed by:1268 members
GMAT Score:770
BTGmoderatorLU wrote:
Fri Feb 05, 2021 3:10 am
Source: GMAT Prep

R is the set of positive odd integers less than 50, and S is the set of squares of the integers in R. How many elements has the intersection of R and S contain?

A. One
B. Two
C. Four
D. Five
E. Seven

The OA is C
So, we need to count all values that satisfy both conditions
In other words, we need to count all values that are BOTH odd integers less than 50 AND are squares of integers

Let's list possible values:
1² = 1 1 is less than 50....keep]
3² = 9 [9 is less than 50....keep]
5² = 25 [25 is less than 50....keep]
7² = 49 [49 is less than 50....keep]
9² = 81 [81 is NOT less than 50.... DON'T keep]

So, the values that satisfy both conditions are: 1, 9, 25, 49
Answer: C

Cheers,
Brent
Brent Hanneson - Creator of GMATPrepNow.com
Image