# Sarin learns Perimeter, Area and Volume in school part 105 (Math Question)

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The blog postings are about the Singapore Math. The readers can learn from the postings about Solving Singapore Primary School Mathematics. The blog presents the Math Concept, the Math Questions with solutions that teaches in Singapore Primary Schools. You or the kids can acquire the skill of dealing with the Math Modeling, the Math Problem Solving and the Problem Sum from Lower Primary School to Upper Primary School level after reading the blog postings. This posting is an upper primary school math question on Ratio and Perimeter

You can read posting Sarin learns Perimeter, Area and Volume in school(Math Concept) to learn the concept of area.

Read the posting on Sarin learns ratio in school (Math Concept) to learn about concept of Ratio.

Read also the posting on Sarin learns Shapes and Solids in school (Math Concept) to know about shapes.

Challenge yourself with the question before look out for the given solution‼!

Upper primary school mathematics question UPQ487

The figure below, not drawn to scale, is made up of 3 semicircles. The diameter of the largest semicircle is 20 cm. find the perimeter of the blue region if the ratio of the diameter of semicircles is 1 : 2 : 4 respectively. (Take π = 3.14)

Solution:

x : y : z = 1 : 2 : 4

4 units = 20 cm

1 unit = 5 cm = x

y = 2 × 5 = 10 cm

y – x = 10 – 5 = 5 cm

The perimeter of the blue region = ½ × 5π + ½ × 10π + 5 = 28.55 cm