To solve problems like this, we must simply break it down and read each part carefully. We can also set it up as a math problem to make it easier to visualize.
The elevator starts on the twentieth floor, so we will represent that with 20.
20
It goes down 11 floors, so we can represent that with a -11.
20-11=9
Now we are on floor 9. Then, we go up 5 floors, so we can represent that with a 5.
9+5=14
Using the math above, we can see the elevator is on the 14th floor.
The measure of the third angle is 50 because a triangle has a sum of 180 degrees by angle.
so... 46+84=130 and to get to 180, the last angle has to be worth 50.
The sample space (list of outcomes) is:
DFNR; DFRN; DRFN; DRNF; DNFR; DNRF;
NFDR; NFRD; NRFD; NRDF; NDRF; NDFR;
RFDN; RFND; RNFD; RNDF; RDFN; RDNF;
FRDN; FRND; FNRD; FNDR; FDRN; FDNR
P(Dave beside Natalie) = 1/2
P(B,G,B,G or G,B,G,B) = 1/3
P(boys in the middle) = 1/6
P(Frida beside Natalie) = 1/2
P(Robbie between Frida & Natalie) = 1/6
P(Natalie between Dave & Robbie) = 1/6
Explanation
Letting D=Dave, R=Robbie, N=Natalie, and F=Frida you get the list of possibilites above.
For P(Dave beside Natalie), look for DN or ND. This appears 12 times out of the 24 possibilities above; 12/24 = 1/2.
For P(B,G,B,G or G,B,G,B), we have the possibilities DFRN, DNRF, RFDN, RNDF, FRND, FDNR, NDFR, NRFD. There are 8 possibilites out of 24; 8/24 = 1/3.
For P(Frida beside Natalie), look for NF or FN. This appears 12 times out of the 24 possibilities; 12/24 = 1/2.
For Robbie between Frida and Natalie, look for FRN or NRF. This appears 4 times out of 24; 4/24 = 1/6.
For Natalie between Robbie and Dave, look for RND or DNR. This appears 4 times out of 24; 4/24 = 1/6.
