A collection of dimes is arranged in a triangular array, with 15 coins in the base row, 14 in the next, 13 in the next, and so forth. Find the value of the collection.
A) $12.00
B) $6.00
C) $1.20
D) $24.00

Question

Quizplus · Accepted Answer

The number of coins in each row forms an arithmetic sequence with a common difference of -1. The first term is 15 and the last term is 1. The sum of an arithmetic sequence is given by the formula:$$S = \frac{n}{2}(a_1 + a_n)$$where n is the number of terms, a1 is the first term, and an is the last term.In this case, n = 15, a1 = 15, and an = 1. Substituting these values into the formula, we get:$$S = \frac{15}{2}(15 + 1) = 120$$Since each coin is worth 10 cents, the value of the collection is $120 x 0.10 = $12.00.

A Collection of Dimes Is Arranged in a Triangular Array