# Sarin learns Shapes and Solids in school part 24 (Math Question)

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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 shapes and angles.

Read the posting on Sarin learns Lines and Angles (Math concept) to understand the concept of lines and angles. Read also the posting on Sarin learns Shapes and Solids in school (Math Concept) to know about shapes.

Upper primary school mathematics question UPQ151

ABC, DEB and CEF are triangles. ABC and DEB are isosceles triangles and CE is a straight line. Find the sum of ACF and DEF.

Solution:

ABC and DEB are isosceles triangles

∠ ACB = ∠ ABC, ∠ DBE = ∠ DEB

CE is a straight line

∠ ABC + ∠ DBE = 1800 – 200 = 1600

∠ ACB + ∠ DEB = 1600

CFE is a triangle

∠ FCE + ∠ CEF = 1800 – 300 = 1500

∠ ACF + ∠ DEF = ∠ ACB + ∠ FCE + ∠ DEB + ∠ CEF

∠ ACF + ∠ DEF = 1600 + 1500 = 3100