OG Green Q76

[umaa]

Today Rose is twice as old as Sam and Sam is 3 years younger than Tina. If Rose, Sam, and Tina are all alive 4 years from today, which of the following must be true on that day?

I. Rose is twice as old as Sam

II Sam is 3 years younger than Tina

III. Rose is older than Tina

A. I only
B. II only
C. III only
D. I and II only
E. II and III only

I chose E.

My explanation:

Assume, R 50.

R=2S
So, S = 25

S = T-3
So, T = 28

After 4 years,

R = 54

S = 29

T = 32

They satisfy both II and III conditions. Let me know if I'm wrong.

[Stuart@KaplanGMAT]

Today Rose is twice as old as Sam and Sam is 3 years younger than Tina. If Rose, Sam, and Tina are all alive 4 years from today, which of the following must be true on that day?

I. Rose is twice as old as Sam

II Sam is 3 years younger than Tina

III. Rose is older than Tina

A. I only
B. II only
C. III only
D. I and II only
E. II and III only

I chose E.

My explanation:

Assume, R 50.

R=2S
So, S = 25

S = T-3
So, T = 28

After 4 years,

R = 54

S = 29

T = 32

They satisfy both II and III conditions. Let me know if I'm wrong.

You answered the question "which of the following COULD be true on that day". However, the question is asking about what "MUST" be true.

If you pick different numbers, you'll see that III is not a MUST be true.

For example, if we let:

R = 2
S = 1
T = 4

we still follow the original rules, but we see that Rose is NOT older than Tina.

Accordingly, only statement II is a "MUST" be true: choose (B).

[umaa]

Got it. Thx..