Selina solutions

Question 1

Q1) In each of the following, find the marked unknown angles :

Solution:

(i) Since sum of all angles of triangle = 180^{\circ}

Hence 70^{\circ}+72^{\circ}+z=180^{\circ}

142^{\ \circ}+z=180^{\ \circ}

z=180^{\ \circ}-142^{\ \circ}

z=38^{\circ}

(ii) Since sum of all angles of triangle = 180^{\circ}

1st triangle 50^{\circ}+80^{\circ}+b=180^{\circ}

130^{\ \circ}+b=180^{\ \circ}

b=180^{\ \circ}-130^{\ \circ}

b=50^{\circ}

2 nd triangle 40^{\circ}+45^{\circ}+a=180^{\circ}

a=180^{\ \circ}-85^{\ \circ}

a=95^{\circ}

(iii) 60^{\circ}+45^{\circ}+20^{\circ}+x=180^{\ \circ}

125^{\circ}+x=180^{\ \circ}

x=180^{\ \circ}-125^{\circ}

x = 55^{\circ}

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