If `m` parallel lines in a plane are intersected by a family of `n` parallel lines, the number of parallelograms that can be formed is a. `1/4m n(m-1)(n-1)` b. `1/4m n(m-1)(n-1)` c. `1/4m^2n^2` d. none of these

Assertion: If m parallel lines are intersected by n other parallel llines, then the number of parallelograms thus formes is (mn(m-1)(n-1))/4 , Reason: A selection of 4 lines 2 form m parallel lines and 2 from n parallel lines givers one parallelogram. (A) Both A and R are true and R is the correct explanation of A (B) Both A and R are true R is not te correct explanation of A (C) A is true but R is false. (D) A is false but R is true.

Straight lines are drawn by joining m points on a straight line of n points on another line. Then excluding the given points, the number of point of intersections of the lines drawn is (no tow lines drawn are parallel and no these lines are concurrent). a. 4m n(m-1)(n-1) b. 1/2m n(m-1)(n-1) c. 1/2m^2n^2 d. 1/4m^2n^2

If 1;m;n are lines in the same plane such that 1 intesects m and n|m ; then 1 intersects n also.

A rectangle with sides of lengths (2n-1) and (2m-1) units is divided into squares of unit length.The number of rectangles which can be formed with sides of odd length,is (a) m^(2)n^(2) (b) mn(m+1)(n+1) (c) 4^(m+n-1) (d) non of these

The number of positive integer pairs (m,n) where n is odd,that satisfy (1)/(m)+(4)/(n)=(1)/(12) is

If m and n are whole numbers such that m^(n)=121, then the value of (m-1)^(n+1) is a 1 b.10 c.1000 d.121