Question

The area of a rectangle of length 21 cm and diagonal 29 cm is __________

Options

• 609 cm²

• 580 cm²

• 420 cm²

• 210 cm²

Answer 1

420 cm² 

Explanation;

Hint:

length = 21 cm

diagonal = 29 cm

By the converse of Pythagoras theorem,

AB² + BC² = AC²

21² + x² = 29²

x² = 841 – 441

400 = 20²

x = 20 cm

Now area of the rectangle = length × breadth.

i.e AB × BC

= 21 cm × 20 cm

= 420 cm²