Chapter 6
Measuring Space: Perimeter and Area
CBSE Class 9
Mathematics Solutions
Educart Mathematics class Class 9 NCERT Exemplar cover
Question:

Two rectangles have the same area and the same perimeter. Does this mean that they are congruent to each other?

Answer: Verified

Yes. If two rectangles have the same area (A) and the same perimeter (P), they must be congruent (meaning their lengths and widths are identical).

Congruent Dimensions:
For rectangles, the Area ( A=l×bA = l \times b ) and Perimeter [P=2(l+b)P = 2(l + b)] systems of equations have only one unique solution for ll and bb .

Unique Shape:
If both l1×b1=l2×b2l_1 \times b_1 = l_2 \times b_2 and 2(l1+b1)=2(l2+b2)2(l_1 + b_1) = 2(l_2 + b_2) , the rectangles must be identical.

Counter-Example Logic:
While a=4×4a = 4 \times 4 square ( A=16A = 16 and P=16P = 16 ) and a=2×6a = 2 \times 6 rectangle ( A=12A = 12 and P=16P = 16 ) have the same perimeter, their areas differ.

If the areas are also forced to be 16, only the 4×44 \times 4 square works, forcing congruence.

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