求助涛涛-28-30

憨憨

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

憨憨

感谢了！！！！

daoying

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.