Question

find the cost of painting a wall with dimension 15 m by 6 m at the rate of Rs.120 per square metre

Answer 1

area of wall(rectangle) = length * breadth 
                  = 15*6
                  =90 m sq.
Cost of painting per sq meter= Rs.120
Cost of painting 90 sq meter =90*120 
                                         = RS.10,800

Answer 2

area of the wall = l*b
                       =15*6
                       =90
cost of painting one sq.mt = 120
cost of painting 90 sq.mt = ? (x)
         (cross multiply)
x = 90*120
   =10800
therefore cost of painting 90 sq.mt is Rs.10.800