Question

Find the length of a diagonal of a rectangle whose side are 21cm and 20cm

Answer 1

Hello Dear !
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Rectangle :
length = 21 cm 
breadth = 20 cm 
Diagonal = ?
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As u know the length and breadth of a rectangle are perpendicular 
So (Diagonal)² = (length )²+( breadth )²
     (Diagonal)² = (21)²  + (20)²
     (Diagonal)² = 441 + 400
     (Diagonal)² = 841 
      diagonal    = 29 cm
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Answer 2

Hello friend

Here's your answer

If we consider the rectangle ABCD and the diagonal DB

We need to find the length of DB

Triangle DAB is right angle triangle

And DB is the diagonal

Using Pythagorean theorem we get

DB^2=AD^2+AB^2

DB^2=20^2+21^2

DB^2=400+441

DB=√841

DB=29cm

Length of the diagonal is 29cm