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2013 WAEC Mathematics Theory The area of a circle is \(154cm^{2}\). It is divided into three sectors such that...

Mathematics
WAEC 2013

The area of a circle is \(154cm^{2}\). It is divided into three sectors such that two of the sectors are equal in size and the third sector is three times the size of the other two put together. Calculate the perimeter of the third sector. [Take \(\pi = \frac{22}{7}\)].

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Explanation

Since it is divide into 3 sectors

  then \(8x° = 360°\)

\(x° = 45°\)

The 3rd sector = 3 times the size of the other two sectors put together

= \(3(45 + 45) = 3(90) = 270°\)

Perimeter of a sector = \(2r + l\)

where r = radius of the circle ; l = length of arc = \(\frac{\theta}{360°} \times 2\pi r\)

Area of circle = \(\frac{22}{7} \times r^{2} = 154 cm^{2}\)

\(r^{2} = \frac{154 \times 7}{22} = 49\)

\(r = 7 cm\)

\(l = \frac{270}{360} \times 2 \times \frac{22}{7} \times 7 = 33 cm\)

Perimeter of sector = \(2(7) + 33 = 14 + 33 = 47 cm\).


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WAEC May/June 2024 - Practice for Objective & Theory - From 1988 till date, download app now - 99995
Post-UTME Past Questions - Original materials are available here - Download PDF for your school of choice + 1 year SMS alerts
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WAEC Past Questions, Objective & Theory, Study 100% offline, Download app now - 24709
WAEC offline past questions - with all answers and explanations in one app - Download for free
WAEC May/June 2024 - Practice for Objective & Theory - From 1988 till date, download app now - 99995
Post-UTME Past Questions - Original materials are available here - Download PDF for your school of choice + 1 year SMS alerts
WAEC Past Questions, Objective & Theory, Study 100% offline, Download app now - 24709