In a stair-like decoration the bottom row has (45) bulbs and each upper row has (3) fewer bulbs. How many bulbs are in the (8)th row?

Correct answer: (24)

The direct answer is B, 24 bulbs. This is an arithmetic progression because the number changes by the same amount in every step. The first row has 45 bulbs, and each row above has 3 fewer, so the common difference is -3. The eighth term is found by counting seven changes after the first row: \(a_8=a_1+(8-1)d=45+7(-3)=45-21=24\). Therefore option B is correct. Option A, 21, would result from subtracting 24, which is too much. Option B, 24, follows the rule exactly. Option C, 27, subtracts only 18 and therefore corresponds to the seventh row, not the eighth. Option D, 30, subtracts only 15 and corresponds to the sixth row. Remember: the first row is already counted, so an eighth term has seven differences.