 Numbers 1 to 9 are grouped in threes so that the smaller two numbers add to the largest number. Each number is to be used once and every number is to be used so let's try one and five yes you six and that those three are used two and three plus four to be seven so those being used and now if we're two plus eight which is not equal to nine but is close so that one doesn't work maybe another way will I really needed the one to go with the eight to make nine maybe the nine's the hardest to make so that's four plus five gives me nine now what else can I use I've used four five nine two plus six equals eight two and six and eight have which leaves me one plus three which does not make sense see if you can fair better can you find those three groups of three numbers