Answer:

Let the common multiple of the given ratio then

∴∠A=5x

∘

and∠B=4x

∘

□ ABCD is a parallelogram.

∴∠A+∠B=180

∘

[Adjacent angle of parallelogram are supplementary]

∴5x+4x=180

∘

⇒9x=180

∘

⇒x=180/9

⇒x=20

∘

∠B=4x=4×20

∘

=80

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The measure of ∠B is 80

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Answer:

Let the common multiple of the given ratio then

∴∠A=5x

and∠B=4x

□ ABCD is a parallelogram.

∴∠A+∠B=180

[Adjacent angle of parallelogram are supplementary]

∴5x+4x=180

⇒9x=180

⇒x=180/9

⇒x=20

∠B=4x=4×20

=80

The measure of ∠B is 80 °