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## 'What's in the Box?' printed from http://nrich.maths.org/

Four numbers in little boxes are put into a special big box that
does a multiplication, then four new numbers come out at the
end:

We only used whole numbers to go in, so, what multiplication might
have gone on in the big box to get the answers in the picture
above?

What was the largest number that could have been used to multiply
by, in that big box?

Imagine four new boxes now (with new numbers in) and the large box
multiplying by a different number this time. The
numbers that come out are these:

What would be the number that the big box is multiplying by?

How are you working these out?

Discuss with others and see if there are different ways that you
found the answers.