Easy DS triangle - Can't get my head around

[Saffa]

Please see attached GMAT prep Question. Should be easy (4th question , but can't get my head aroundit.

[parallel_chase]

refer this

https://www.beatthegmat.com/angles-gprep-t14992.html

[Saffa]

refer this

https://www.beatthegmat.com/angles-gprep-t14992.html

I don't understand your explanation. With S = 90, "Therefore the remaining two angles can be 60, 30." Why would the other two angles be 30 and 60 and not any combination of numbers where the sum wil be 90 (ie. 45, 45 or 5, 85)?

[parallel_chase]

Here is the process:

question stem : PRS - PQR = ?

Statement I
QPR = 30
QPR + PQR + PRQ = 180
PQR + PRQ = 180-30 = 150

PRQ = 150 - PQR

PRS + PRQ = 180 [ANGLES FORMED IN STRAIGHT LINE]

PRS + 150 - PQR = 180

PRS - PQR = 180-150 = 30

Sufficient.


Statement II

PQR + PRQ = 150

PRQ = 150-PQR

PRS + PRQ = 180 [ANGLES FORMED IN STRAIGHT LINE]

PRS + 150-PQR = 180

PRS - PQR = 180 -150 = 30

Sufficient.

Hence D.

My earlier explanation seems bit off track, dont know what I was thinking. :roll:

Hope this explanation helps.