child must discover for himself that if, for example, 2 X 75 = 150, then 2 x 74 must equal 150 - 2, or 148. Until he does, no amount of talk will enable him to make that step, far less make use of this understanding to see that since 3 X 50 = 150, 3 X 49 must equal 150 -- 3, or 147.
