[求助]gwd-28-30

exhilarating

Q30:

A rectangular photograph is surrounded by a border that is 1 inch wide on each side.  The total area of the photograph and the border is M square inches.  If the border had been 2 inches wide on each side, the total area would have been (M + 52) square inches.  What is the perimeter of the photograph, in inches?

 

 

A.      34

B.      36

C.      38

D.     40

E.      42

I can only until

xy=M

(x+1)(y+1)=M+52

(x+1)(y+1)-xy=52

(x+2)y-xy=52

and solve x=25, y=26.

But can't find the perimeter=40, which is D.

Can anyone please help?

Thank you very much.

exhilarating

 But according to , x=25, y=26, the answer is 2(25+26)=82

how come?

IORIYAGAMI

(x+1)*(y+1) = M; (x+2)*(y+2) = M + 52

exhilarating

这样算下来， x+y=49, 所以photograph的周长是98， 那位xdjm给验算一下。感谢！！

shawlen

(X+2)(Y+2)=M,(X+4)(Y+4)=M+52,

2(X+Y)=40