How many triangles and quadrilaterals altogether can be formed using the vertices of a 7-sided regular polygon?

a. 35
b. 40
c. 50
d. 65
e. 70

 The correct option is

(E) 70.

Step-by-step explanation:  We are given to find the number of  triangles and quadrilaterals altogether that can be formed using the vertices of a 7-sided regular polygon.

To form a triangle, we need any 3 vertices of the 7-sided regular polygon. So, the number of triangles that can be formed is

Also, to form a quadrilateral, we need any 4 vertices of the 7-sided regular polygon. So, the number of quadrilateral that can be formed is

Therefore, the total number of triangles and quadrilaterals is

Thus, option (E) is CORRECT.

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step-by-step explanation: