求助涛涛-28-30

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

答案为D.算来算去算不到选项中答案,那位高手，烦劳给与指点。谢谢

Suppose one side of the rectangular is x and the other side is y.

First area: M=(x+1*2)(y+1*2)=xy+2(x+y)+4

Second area: M+52=(x+2*2)(y+2*2)=xy+4(x+y)+16

Take the difference of the two equations => 52=2(x+y)+12 => perimeter=2(x+y)=40.

thanks

 had been 2 inches 我就是看错了这个，认为是加2inch

读题一定要小心