NPR Sunday Puzzle (Jan. 3, 2010): It All Adds Up to a New Year:
Q: Write down the digits from 2 to 7, in order. Add two mathematical symbols to get an expression equaling 2010. What symbols are these?
Yippee! A math puzzle for 2010. The most obvious question is, do you need to get fancy with symbols beyond the standard operations of multiplication, division, addition and subtraction? For example, do you need to use a decimal point, factorials, exponentiation, square roots, etc.? Would Will be so diabolical or would he start us off easy in 2010?
I will say, using just the standard four operations between the digits, you can get 160 different results (4 x 4 x C(5,2) = 160). Of these results, 69 are positive integers. Once you have solved the puzzle for 2010, have fun seeing if you can create any of these results: 1, 623, 1102, 1103, 2291, 4572 or 4573. Also, what's the largest number you can create with just the standard operations?
Edit: The largest number you can form is 2345x6x7 = 98,490. If you study that number you'll see it is 49 times the desired solution of 2010. So just divide by 7 instead of multiplying.
A: 2345 x 6 / 7 = 2010