Answer: (d) 27
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Reason:
The four numbers are OLYM, LOMY, YMOL, and MYLO.
The units digits of each of those are M, Y, L, and O in that order.
Adding those units digits will produce either a one or two digit number. Either way, the result will involve a units digit that matches the units digit of the sum 29997. In that case it's 7.
Therefore, the answer must have a units digit of 7. The only answer choice possible is choice (d).
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Examples:
OLYM + LOMY + YMOL + MYLO = 3798+7389+9837+8973 = 29997
O + L + Y + M = 3 + 7 + 9 + 8 = 27
and
OLYM + LOMY + YMOL + MYLO = 4698+6489+9846+8964 = 29997
O + L + Y + M = 4 + 6 + 9 + 8 = 27
and
OLYM + LOMY + YMOL + MYLO = 5796+7569+9657+6975 = 29997
O + L + Y + M = 5 + 7 + 9 + 6 = 27
I used computer software to generate these examples. There are others.