how many paying stones , each measuring 2 1 / 2 m * 2 m are required to pave a rectangular court yard 20 m long and 16 1 / 2 m board ?
"20 * 33 / 2 = 5 / 2 * 2 * x = > x = 66 answer : a"
divide(multiply(20, add(16, divide(1, 2))), multiply(add(2, divide(1, 2)), 2))