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If the length of a rectangle is thrice its breadth and the perimeter of that rectangle is 48┬аcm, then find its area (in cm2).
84
112
108
96
108
Since L=3B, the semi-perimeter P/2=4B=24. Thus, B=6 and L=18. The area is 18├Ч6=108.
Perimeter of rectangle = 48 cm, Length (L) = 3 ├Ч Breadth (B)
P=2(L+B), A=L├ЧB
Since L=3B, the semi-perimeter P/2=4B=24. Thus, B=6 and L=18. The area is 18├Ч6=108.
Confusing area and perimeter formulas or forgetting the factor of 2 in the perimeter equation (P=2(L+B) vs P=L+B).
Define dimensions
Let the breadth of the rectangle be B. Given that the length L is thrice the breadth, we have L=3B.
L=3B
Use perimeter formula
The perimeter of a rectangle is given by P=2(L+B). Substituting 48 for P and 3B for L:
48=2(3B+B)
Solve for Breadth (B)
Simplify the equation: 48=2(4B), which means 48=8B. Dividing by 8 gives B=6.
B=6┬аcm
Calculate Length (L)
Using L=3B, we find the length: L=3├Ч6=18.
L=18┬аcm
Calculate Area (A)
The area is the product of length and breadth: A=L├ЧB=18├Ч6=108.
A=108┬аcm2
C is correct because calculations yield length 18 cm and breadth 6 cm, resulting in an area of 108 cm┬▓.
This relates to ratio-based geometry problems often found in exams; always establish a single-variable relationship first.