Missing Addend Detective

About Missing Addend Detective

Missing Addend Detective puts the blank in the middle instead of at the end. A child who can answer 7 plus 5 without hesitating will often stall completely on 7 plus what makes 12, and the reason that happens is worth understanding: they have learned addition as an instruction to carry out from left to right rather than as a relationship between three numbers that can be read in any direction. Putting the unknown where the answer usually goes forces the relationship into view, and it is exactly the move that makes algebra survivable several years later, when the unknown stops being a blank box and becomes a letter. Solving these also quietly rehearses subtraction, because finding what to add to seven to reach twelve is the same question as twelve take away seven, and children who meet both forms early stop treating the two operations as unrelated subjects. From the third level the blank sometimes leads the equation instead of following the known number, which stops any recipe from forming — a child who has learned to always subtract the first number they see will be caught out, and that is the point of the variation rather than an accident of it. Totals grow with the level and stay within twenty. Four large answer buttons sit close together in value so a near miss can be told apart from a guess. Wrong answers cost nothing and move on with encouragement. The game is free, runs in any browser, needs no sign-up, shows no advertising to children, and keeps progress on the device.