The blog postings are about the Singapore Math. The readers can learn from the postings on Solving Singapore Primary School Mathematics. You or your kids can learn dealing with Math modeling, Problem Sum from Lower Primary School to Upper Primary School level in Singapore school. This posting is a primary school math question on perimeter, fraction and decimal number.

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

Read also the posting on **Sarin learns Shapes and Solids in school (Math Concept)** to know about shapes and the posting on **Sarin learns Lines and Angles (Math concept) **to understand the concept of lines and angles. As well as reading the posting on **Sarin and the million numbers (Math concept )** on decimal number.

You can click and read also the posting on **Sarin learns Concept of Fraction in school** to learn about Portion or Fraction and read the posting on **Sarin learns concept of ratio in school** to understand mathematics concept of Ratio..

Upper primary school mathematics question UPQ156

AB and CD are diameters of a bigger circle. EF and GH are diameters of a smaller circle. O is the centre for both circles. Find the perimeter of the figure. Round off the answer to 1 decimal place. (Use π = 3.14159)

Solution:

A circle measured 360^{0 }

Centre point is at O for both the circles

The circle is portion out to 40^{0}, 140^{0}, 40^{0}, 140^{0}

In term of fraction is 40/360 = 1/9, 140/360 = 3.5/9, 1/9 and 3.5/9

The length of Arc AD + Arc BC = 2 × 7 × π × 2/9 = 9.77cm

The length of Arc EG + Arc HF = 2 × 3 × π × 7/9 = 14.66cm

The length of Line AE + Line GC + Line DH + Line FD = 4 × 4 = 16cm

The perimeter of the figure = 9.77 + 14.66 + 16 = 40.4cm

Alternative solution:

Work out using fraction and ratio

Draw a fraction model on the small circle

The length of Arc EG + Arc HF = 2 × 3 × π × 7/9 = 14.66cm

7 units = 14.66

1 unit = 2.09cm

The length of Arc EH + Arc GF = 2 × 2.09 = 4.18cm

Ratio of Arc AD to Arc EH = 3 : 7

3 units = 4.18

1 unit = 1.39cm

The length of Arc AD + Arc BC = 7 × 1.39 = 9.75cm

The length of Line AE + Line GC + Line DH + Line FD = 4 × 4 = 16cm

The perimeter of the figure = 9.75 + 14.66 + 16 = 40.4cm