If the operation @ is defined by x @ y = sqrt(xy) for all positive numbers x and y, then (5 @ 45) @ 60 =
A) 30
B) 60
C) 90
D) 30sqrt(15)
E) 60sqrt(15)
OA: A
A) 30
B) 60
C) 90
D) 30sqrt(15)
E) 60sqrt(15)
OA: A
I call these "Strange Operator" questions.boomgoesthegmat wrote:If the operation @ is defined by x @ y = √(xy) for all positive numbers x and y, then (5 @ 45) @ 60 =
A) 30
B) 60
C) 90
D) 30√15
E) 60√15
OA: A
We want to evaluate: (5 @ 45) @ 60
Start with (5 @ 45)
(5 @ 45) = √[(5)(45)]
= √225
= 15
So, (5 @ 45) @ 60 = 15 @ 60
From here, 15 @ 60 = √[(15)(60)]
= √900
= 30
Answer: A
RELATED RESOURCE (video)
- Strange operators: https://www.gmatprepnow.com/module/gmat ... /video/976
- Additional practice: https://www.gmatprepnow.com/module/gmat ... /video/977
Cheers,
Brent
