Final answer:
To estimate the total cost of 3 CDs priced at $12.89 each, round the price to $13 per CD and multiply by the quantity, resulting in an estimated cost of $39.
Step-by-step explanation:
If a student wants to buy 3 CDs for $12.89 each and needs to estimate the total cost, we start by rounding the cost of one CD to the nearest dollar, which is $13. Multiplying this estimated price by the quantity gives us an estimated total:
$13 × 3 CDs = $39
Therefore, the estimated total cost for the 3 CDs is about $39, which corresponds to option D.