Question 12 - Figure it out - Page 185 to 189 - Chapter 7 Class 7 - Finding the Unknown (Ganita Prakash II)

Transcript

Question 12 Find the measures of the angles of these triangles.Let’s do this one by one Let’s do this one by one First Figure Here, we can use the isosceles triangle theorem Angles opposite equal sides is equal Thus, Third angle = y + 15 Also, by Angle Sum Property of triangle Sum of angles of a triangle = 180° y + (y + 15) + (y + 15) = 180 (y + y + y) + (15 + 15) = 180 3y + 30 = 180 Putting 30 on right side, it becomes –30 3y = 180 – 30 3y = 150 Putting 3 on right side, so it becomes division y = 150/3 y = 50 Thus, all three angles are First angle = y = 50° Second angle = y + 15 = 50 + 15 = 65° Third angle = y + 15 = 50 + 15 = 65° Second Figure Here, all three angles are given By Angle Sum Property of triangle Sum of angles of a triangle = 180° x + (x – 10) + (x + 10) = 180 (x + x + x) + (–10 + 10) = 180 3x + 0 = 180 3x = 180 Putting 3 on right side, so it becomes division x = 180/3 x = 60 Thus, all three angles are First angle = x = 60° Second angle = x – 10 = 60 – 10 = 50° Third angle = x + 10 = 60 + 10 = 70°