PowerPrep Question

[kuemura]

In the isociles triangle RST, what is the measurement of angle R?

(1) Measurement of angle T is 100
(2) Measrument of angle S is 40

Answer is A. I thought D.

What am I missing here? Can anyone explain?

[eravi11]

ok..what u might have misunderstood or i would say have overlooked is that another angle could also be 100 which is certainly not possible..sum of angles of triangle=180..

thus with statement 1,it is sufficeint that in isoceles triangle angle R and S will be equal

so x+x=180-100
=>x=40.

with statement 2: I can't find which angles are equal thus it's inusfficient..

[Fiver]

1] The only possibility of measure for angle R,S & T is 40-40-100
2] The possibilities of measure for angle R,S & T are: 40-40-100, 70-40-70, 100-40-40 & 40-40-100. Diff values for angle R; hence insuff.
A is the answer.

[clock60]

agree with A...

[kuemura]

Thanks Guys!

[touche]

Isosceles....
1. one angle 100..... obviously the third as it cant have two angles 100. (180-100)/2=40 suff
2. one angle 40.... other 2 could be 70 each or 40 and 100... insuff
A