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## 'One Wasn't Square' printed from http://nrich.maths.org/

Mrs Morgan, the class's teacher, pinned numbers onto the backs
of three children: Mona, Bob and Jamie.

"Now", she said, "Those three numbers add to a special kind of
number. What is it?"

Michael put his hand up.

"It's a square number", he answered.

"Correct", smiled Mrs Morgan.

"Oh!" exclaimed Mona, "The two numbers I can see also add to a
square!"

"And me!" called out Bob, "The two numbers I can see add to a
square too!"

"Oh dear", said Jamie disappointedly, "the two numbers I can see
don't add to a square! It's either $5$ too little or $6$ too
big!"

What numbers did the three children have on their backs?