Bunuel
A photograph rectangular in shape is surrounded by a border that is 2 centimeters wide on each side. The combined area of the photograph and the border is a square inches. Had the border been 4 centimeters wide on each side, the total area would have been (a + 100) square centimeters. What is the perimeter, in centimeters, of the photograph?
(A) 18
(B) 20
(C) 24
(D) 26
(E) 52
Please look at the figure below :
The green area is the border
Attachment:
GMAT photograph.png [ 7.1 KiB | Viewed 4286 times ]
The length of the photograph is \(a\) and width is \(b\).
Hence perimeter will be \(2(a+b)\)
When the border is \(2\) cms :
The combined length becomes \(a+4\) and combined width becomes \(b+4\)
Hence area
\((a+4 )(b+4) =a\)
\(ab +4a +4b+16 =a (i)\)
When the border is \(4\) cms :
The combined length becomes \(a+8\) and combined width becomes \(b+8\)
Hence area:
\((a+8 )(b+8 ) =( a+100)\)
\(ab+8a+8b+64 = a+100 (ii)\)
\((ii)-(i) \)
\(4a+4b +48=100\)
\(4a+4b=52\)
\(a+b=13\)
\(2(a+b)=26 =\) Perimeter
Ans=D
Hope it's clear.