math
posted by margret .
A collection of dimes is arranged in a triangular array with 14 coins in the base row, 13 in the next, 12 in the next, and so forth. Find the value of the collection.

number of dimes
= 1+2+3+...+13+14
= 7(1+14) = 105
value = 105(.10) = $10.50