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JAMB Mathematics 2020 Paper

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Question : 37

Total: 40

The sum of the interior angle of pentagon is 6x + 6y. Find y in terms of x.

y = 6 - x
y = 90 - x
y = 120 - x
y = 150 - x

Solution:

Concept:

The sum of the interior angles of an

n

-sided polygon is

(2n - 4) \times 90^\circ

.

Explanation:

For a pentagon,

n = 5

.

Sum of interior angles

= (2(5) - 4) \times 90^\circ = 6 \times 90^\circ = 540^\circ

.

Given:

6x + 6y = 540^\circ

.

Divide both sides by

6

:

x + y = 90^\circ

.

Make

y

the subject:

y = 90^\circ - x

.

So, in terms of

x

,

y = 90 - x

.

Answer:

y = 90 - x

Option B.

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