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If $a\times b=2$, $b\times c=24$, $c\times a=3$ and $a$, $b$ and $c$ are all positive, what is the value of $a+b+c$?
If you liked this problem, here is an NRICH task which challenges you to use similar mathematical ideas.
Take any pair of two digit numbers x=ab and y=cd where, without loss of generality, ab > cd . Form two 4 digit numbers r=abcd and s=cdab and calculate: {r^2 - s^2} /{x^2 - y^2}.
The nth term of a sequence is given by the formula n^3 + 11n. Find the first four terms of the sequence given by this formula and the first term of the sequence which is bigger than one million. Prove that all terms of the sequence are divisible by 6.