SOLUTION: a number 1 to 9 digits it can be eg 1+2-34etc and the numbers should not be repeated but the answer should be =100
Algebra ->
Permutations
-> SOLUTION: a number 1 to 9 digits it can be eg 1+2-34etc and the numbers should not be repeated but the answer should be =100
Log On
The first 7 counting numbers 1,2,3,4,5,6,7
average to their middle number 4, so they add to 7×4 or 28.
Then the next two, 8×9 = 72 and 28+72=100. So:
1+2+3+4+5+6+7+8×9 = 100
28+72 = 100
Edwin