Qrt questions

[sunny2004]

please give equations for these if you know
1.Jill has six different books In how many ways can Jill select two different books?
2. a painting which is 4 ft. wide and 5 ft. long is surrounded by a rectangular frame 6inchs wide .what percent of the area of the picture and the frame is occupied by the frame?

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[kumjohn]

please give equations for these if you know
1.Jill has six different books In how many ways can Jill select two different books?
nCr = n! / (n-r)! r!
= 6! / (6-2)! 2!
= 6*5*4! / 4! 2!
= 15

2. a painting which is 4 ft. wide and 5 ft. long is surrounded by a rectangular frame 6inchs wide .what percent of the area of the picture and the frame is occupied by the frame?

12 inchs = 1 ft.
area of painting = 4ft * 5ft
= 20 ft^2

area of frame = 5ft * 6ft( plus 12inchs on each side)
= 30 fr^2

% of area occupied by frame = (30 - 20) / 30 *100
= 33.33

 

[sunny2004]

thanks kumjohn

 

[golf10s]

Wrong forum

 

[golf10s]

Originally posted by sunny2004
please give equations for these if you know
1.Jill has six different books In how many ways can Jill select two different books?

Originally posted by kumjohn
please give equations for these if you know
1.Jill has six different books In how many ways can Jill select two different books?
nCr = n! / (n-r)! r!
= 6! / (6-2)! 2!
= 6*5*4! / 4! 2!
= 15

kumjohn, you're correct in your explanation but you stopped at half point. This question is # 38 of the DAT Program Booklet, am I right sunny2004? The real answer is 30, NOT 15. The use of the 2 factorials is correct but you have to remember that you can choose the books in either way. Meaning, 4 ways are : book1-book2, 1-3, 1-4, 1-5. But the other 4 ways are using the same books, but in the opposite order : 5-1, 4-1, 3-1, 2-1. Thus, if you do that for all books, you get 15 x 2 = 30 ways.

Hope that helps.

kumjohn, I wasn't trying to put you down so you know. Just thought I'd correct it so sunny2004 will have the correct answer going into DAT.

 

[golf10s]

Third expansion factor of (x + 3)^5 is 90x^3 because (x + 3)^5 = (x + 3)(x + 3)(x + 3)(x + 3)(x + 3) = x^5 + 15x^4 + 90x^3 + 260x^2 + 375x + 243 and they were looking for the THIRD factor after you foil everything out.

Don't worry. I'm not this smart. My brother who's an electrical engineer solved the problem for me. It just seemed like noone was getting it because of the technical term use. We all know how to FOIL but just didn't know what "expansion factor" meant.

Hope that helps.