If 3 dozen eggs cost Rs 90 , find the cost of 3 scores of eggs [1 score = 20]
We know that
3 dozen = $$ 3 \times 12 = 36 eggs $$
3 scores = $$ 3 \times 20 = 60 eggs $$
Cost of 36 eggs = Rs 90
Cost of 1 eggs = Rs 90/36
Cost of 60 eggs $$ = \dfrac{\left ( 90 \times 60 \right ) }{36 }= Rs 150 $$