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Angles in a Triangle

Can you work out the size of the angle marked with a letter in the given triangles?

Menu Level 1 Level 2 Point Parallels Polygons Circles Help More
No calculator

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.

41o

48o

Working:

a=o Correct Wrong

79o

33o

Working:

b=o Correct Wrong

145o

129o

Working:

c=o Correct Wrong

48o

42o

Working:

d=o Correct Wrong

55o

43o

Working:

e=o Correct Wrong

77o

139o

Working:

f=o Correct Wrong

43o

38o

Working:

g=o Correct Wrong

15o

44o

Working:

h=o Correct Wrong

48o

48o

Working:

i=o Correct Wrong

29o

29o

Working:

j=o Correct Wrong
Check

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

Instructions

Try 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.org

This 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.

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"An absolutely brilliant resource. Only recently been discovered but is used daily with all my classes. It is particularly useful when things can be saved for further use. Thank you!"

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Featured Activity

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This activity comprises of five challenges each one requiring you to type in one more fraction than the previous challenge and each starting with a different fraction. The starting fractions are one tenth, one quarter, one third, one half and four sevenths.

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Learning 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.

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Are 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.

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Description of Levels

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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 self-marking exercises.

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.

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Help

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 double-click 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.

Log in Sign up

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