Question

The number of parallelograms that can be formed from a set of four parallel lines intersecting another set of three parallel lines is: 

(a) 18 

(b) 12 

(c) 9 

(d) 6

Answer 1

(a) 18

To form a parallelogram we need 2 parallel lines from 4 and 2 intersecting lines from 3. 

Number of parallelograms = 4C₂ x 3C₂

= \(\frac{4\times3}{2\times1}\) _{x 3}

= 18