Question

find the perimeter of rectangle whose length is 40 cm and di agonl is 41. for seventh class

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Answer 1

Step-by-step explanation:

length= 41 and diagonal = 41

then breadth^2 = (41)^2 - (40)^2 (by Pythagoras theorem)

=81 =9^2

breadth= 9

perimeter =2(l+b)

=2(40+9) = 2×49 =98 cm

Answer 2

GIVEN :-

• Length of rectangle , CD = 40 cm.
• diagonal of rectangle , BD = 41 cm.

TO FIND :-

• The perimeter of rectangle.

SOLUTION :-

• [ Now, for calculating the breadth of the rectangle we have to use the Pythagoras theorem in triangle (⊿) BCD ]

★ By Pythagoras theorem in⊿BCD ★

→ (BC)² + (CD)² = (BD)²

→ (BC)² + (40)² = (41)²

→ (BC)² + 1600 = 1681

→ (BC)² = 1681 - 1600

→ (BC)² = 81

→ BC = √81

→ BC = 9

★ Hence the breadth of the rectangle , BC is 9 cm.

• [ Now , for calculating the perimeter of the rectangle we have to apply the formula , perimeter = 2(Length + Breadth ]

★ Perimeter = 2(Length + Breadth)

→ 2(40 cm + 9 cm)

→ 2(49 cm)

→ 2 × 49 cm

→ 98 cm

★ Hence perimeter of the rectangle is 98 cm.