Join 60,000+ competitive exam aspirants
If the length of a rectangle is 12 cm and the diagonal is 13 cm, what is the area of the rectangle?
60┬аsq┬аcm
72┬аsq┬аcm
50┬аsq┬аcm
65┬аsq┬аcm
60┬аsq┬аcm
Recognize the standard Pythagorean triplet (5, 12, 13) immediately to find the breadth as 5 cm without doing full algebraic expansion.
Length of rectangle l=12 cm and diagonal d=13 cm
d=l2+b2тАЛ, Area=l├Чb
Recognize the standard Pythagorean triplet (5, 12, 13) immediately to find the breadth as 5 cm without doing full algebraic expansion.
Confusing the diagonal of a rectangle with its perimeter or directly multiplying length by diagonal instead of finding the breadth first.
Identify Given Parameters
We are given the length l=12 cm and the diagonal d=13 cm of the rectangle.
l=12┬аcm,d=13┬аcm
Find the Breadth Using Pythagoras Theorem
The relationship between length, breadth, and diagonal of a rectangle is given by d2=l2+b2. Substituting the values: 132=122+b2.
169=144+b2
Calculate the Breadth
Solving for b2, we get b2=169тИТ144=25. Therefore, the breadth b=5 cm.
b=25тАЛ=5┬аcm
Calculate the Area of the Rectangle
The area of a rectangle is the product of its length and breadth: Area=l├Чb=12├Ч5.
Area=12├Ч5=60┬аsq┬аcm
A is correct because the calculated area of the rectangle is 60 sq cm.
Pythagorean triplets frequently simplify geometry problems in competitive exams, saving valuable time in quantitative aptitude sections.