Question

the area of a rectangle of length 21 cm and diagonal 29 cm is centimetre square​

Answer 1

Answer:

By Pythagoras therom b=20cm as we know area of rectangle is Lb area = 20*21=420sq.cm

Answer 2

The area of a rectange =  420 $cm^{2}$

Step-by-step explanation:

Given,

The length of rectangle (l) = 21 cm and

The diagonal of of rectangle (d) = 29 cm

Let the breadth of rectangle  = b cm

To find, the area of a rectange = ?

We know that,

The diagonal of of rectangle = $\sqrt{l^{2}+b^{2}}$

⇒ $\sqrt{21^{2}+b^{2}}$ = 29

Squaring both sides, we get

⇒ $21^{2}+b^{2}=29^2$

⇒ $b^{2}$ = 841 - 441 = 400

⇒ $b^{2}$ = $20^{2}$

∴ The breadth of rectangle  = 20 cm

The area of a rectange = Length(l) × Breadth (b)

= 21 cm × 20 cm

= 420 $cm^{2}$

Thus, the area of a rectange =  420 $cm^{2}$