Angles in a TriangleCan you work out the size of the angle marked with a letter in the given triangles? 
This is level 2: more interesting problems about the angles in triangles. You can earn a trophy if you get at least 7 questions correct and you do this activity online.
This is Angles in a Triangle level 2. You can also try:
Level 1
The last question in level 2 is inspired by a question from the 2011 UK INTERMEDIATE MATHEMATICAL CHALLENGE
InstructionsTry your best to answer the questions above. Type your answers into the boxes provided leaving no spaces. As you work through the exercise regularly click the "check" button. If you have any wrong answers, do your best to do corrections but if there is anything you don't understand, please ask your teacher for help. When you have got all of the questions correct you may want to print out this page and paste it into your exercise book. If you keep your work in an ePortfolio you could take a screen shot of your answers and paste that into your Maths file. 



Transum.orgThis web site contains over a thousand free mathematical activities for teachers and pupils. Click here to go to the main page which links to all of the resources available. Please contact me if you have any suggestions or questions. 
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Mathematicians are not the people who find Maths easy; they are the people who enjoy how mystifying, puzzling and hard it is. Are you a mathematician? Comment recorded on the 23 September 'Starter of the Day' page by Judy, Chatsmore CHS: "This triangle starter is excellent. I have used it with all of my ks3 and ks4 classes and they are all totally focused when counting the triangles." Comment recorded on the 18 September 'Starter of the Day' page by Mrs. Peacock, Downe House School and Kennet School: "My year 8's absolutely loved the "Separated Twins" starter. I set it as an optional piece of work for my year 11's over a weekend and one girl came up with 3 independant solutions." 
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AnswersThere are answers to this exercise but they are available in this space to teachers, tutors and parents who have logged in to their Transum subscription on this computer. A Transum subscription unlocks the answers to the online exercises, quizzes and puzzles. It also provides the teacher with access to quality external links on each of the Transum Topic pages and the facility to add to the collection themselves. Subscribers can manage class lists, lesson plans and assessment data in the Class Admin application and have access to reports of the Transum Trophies earned by class members. If you would like to enjoy adfree access to the thousands of Transum resources, receive our monthly newsletter, unlock the printable worksheets and see our Maths Lesson Finishers then sign up for a subscription now: Subscribe 

Go MathsLearning and understanding Mathematics, at every level, requires learner engagement. Mathematics is not a spectator sport. Sometimes traditional teaching fails to actively involve students. One way to address the problem is through the use of interactive activities and this web site provides many of those. The Go Maths page is an alphabetical list of free activities designed for students in Secondary/High school. Maths MapAre you looking for something specific? An exercise to supplement the topic you are studying at school at the moment perhaps. Navigate using our Maths Map to find exercises, puzzles and Maths lesson starters grouped by topic.  
Teachers  
If you found this activity useful don't forget to record it in your scheme of work or learning management system. The short URL, ready to be copied and pasted, is as follows: 
Alternatively, if you use Google Classroom, all you have to do is click on the green icon below in order to add this activity to one of your classes. 
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Scan the QR code below to visit the online version of this activity.
https://Transum.org/go/?Num=143
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It is assumed that the angles together on a straight line theorem is already known.
Level 1  Find the marked angle in the triangle diagrams
Level 2  More interesting problems about the angles in triangles
Angles at a point  Apply the properties of angles at a point, angles on a straight line and vertically opposite angles.
Angles with Parallel Lines  Understand and use the relationship between parallel lines and alternate and corresponding angles.
Polygon Angles  Practise the skills of finding interior and exterior angles of polygons to answer these questions.
Angles in Circles  Show that you understand the circle theorems with this self marking exercise.
More Angle Resources  including lesson Starters, visual aids, investigations and selfmarking exercises.
The diagrams are not drawn to scale but lines that look like straight lines can be taken as straight lines.
Don't wait until you have finished the exercise before you click on the 'Check' button. Click it often as you work through the questions to see if you are answering them correctly. You can doubleclick the 'Check' button to make it float at the bottom of your screen.
The boxes made available to show working don't have to be used. It would be better to set out your working neatly in you exercise book but that may not always be practical.
+ The blue button allows you to add extra lines of working.
Please note that when the system marks your answers the working is not taken into consideration.
Answers to this exercise are available lower down this page when you are logged in to your Transum account. If you don’t yet have a Transum subscription one can be very quickly set up if you are a teacher, tutor or parent.
These exercises use MathQuill, a web formula editor designed to make typing Maths easy and beautiful. Watch the animation below to see how common mathematical notation can be created using your keyboard.
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