Sarin learns Shapes and Solids in school part 54 (Math Question)

Standard

The blog postings are about the Singapore Math. The readers can learn from the postings on 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 learn the skills to deal 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 Angles and Shapes.

Read the posting on Sarin learns Lines and Angles (Math concept) to understand the concept of lines and angles.

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

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

Upper primary school mathematics question UPQ456

In the figure below, no drawn to scale, C is the centre of the circle. AB is the straight line. CD and EC is the radius of the circle.  DCB = 720 and EA = EC. Find the value of  ECD.

UPQ456-1

Solution:

            CD and EC are radius of the circle,

            CD = CE = EA

            AEC form a isosceles triangle AEC with EA = EC

              EAC =   ECA

              DEC is exterior of triangle AEC

              DEC =   EAC +   ECA = 2 ×   EAC

            EDC form a isosceles triangle ECD with CE = CD

              EDC =   DEC = 2 ×   EAC = 2 ×   ECA

              ECD = 1800 – 2 ×   EDC = 1800 – 4 ×   ECA

            AB is a straight line

              ECA +   ECD + 720 = 1800

              ECA + 1800 – 4 ×   ECA + 720 = 1800

            3 ×   ECA =720

              ECA = 240

              ECD = 1800 – 4 × 240 = 840

 More Questions on Lines, Shapes and Angles. Click here….

Advertisements

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s