This blog is managed by Song Hock Chye, author of Improve Your Thinking Skills in Maths (P1-P3 series), which is published and distributed by EPH.

Wednesday, September 07, 2011

Hokkien Huay Kuan Combined Primary 2010 PSLE Math Prelim Paper 2 Q13

The figure below shows 2 quarter circles and a rectangle. The radius of the big quarter circle is 8 cm. The radius of the small quarter circle is 4 cm. Find the difference in area between the two shaded parts of X and Y. Use the calculator value of pi and give your answer correct to 1 decimal place.


Area of rectangle ----- 8 cm x 4 cm = 32 square cm

Area of large quadrant -----
(1/4) x pi x 8cm x 8 cm
= 16(pi) square cm

Area of small quadrant ------
(1/4) x (pi) x 4cm x 4cm
= 4(pi) square cm

Area of Large quadrant - Area of small quadrant -----
16(pi) square cm - 4(pi) square cm
= 12(pi) square cm

Difference between the two shaded parts X and Y -----
(12 x pi) square cm - 32 square cm
approximately ----- 5.7 square cm

Answer: 5.7 square cm

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