S’pore Hokkien Huay Kuan 2007 PSLE Math Prelim Q43

The figure below is made up of a semicircle and a rectangle. Find the area of the unshaded region.






Solution

The base of the figure is 28 cm. The diameter of the unshaded circle is half the base, hence, it is 14 cm. This also means that the radius of the circle is 7 cm.

The radius of the 2 quadrants is 14 cm.

Area of circle ----- 22/7 x 7 cm x 7 cm = 154 square cm

Area of 1 quadrant ----- 22/7 x 14 cm x 14 cm x ¼ = 154 square cm

Area of 2 quadrants ----- 154 square cm x 2 = 308 square cm

Total unshaded area ----- (154 + 308) square cm

= 462 square cm (Answer)

Note – “The Singapore Hokkien Huay Kuan 5-School Combined Prelim Maths” is the common Maths Prelim Exam for Tao Nan, Ai Tong, Chongfu, Nan Chiau and Kong Hwa schools.