What 6 digit combinations can you make using the numbers 2 7 8 9 repeating two of the numbers?
There are 48 combinations. These are:
222277, 222288, 222299, 227777, 228888, 229999,
777788, 777799, 778888, 779999, 888899, 889999,
222777, 222888, 222999, 777888, 777999, 888999,
227789, 227889, 227899, 277889, 277899, 278899,
222778, 222779, 222788, 222799, 222889, 222899,
227778, 227779, 277788, 277799, 777889, 777899,
227888, 228889, 277888, 288899, 778889, 788899,
227999, 228999, 277999, 288999, 778999, 788999.
All four digits are not used in each combination but that was
not required by the question.