To find the area of the postcard, we can use the formula for the area of a rectangle, which is length multiplied by width.
The problem states that the length of the postcard is 15 centimeters. Since the original photo has a length-to-width ratio of 6 cm by 4 cm, we can find the width of the postcard by maintaining that same ratio.
First, let's find the ratio of the original dimensions: \[ \text{Ratio} = \frac{6 \text{ cm}}{4 \text{ cm}} = \frac{3}{2} \]
Now, if the length of the postcard is 15 cm, we can find the width using the ratio: Let the width be \( w \). Then we have: \[ \frac{15}{w} = \frac{3}{2} \]
Cross-multiply to solve for \( w \): \[ 3w = 30 \ w = 10 \text{ cm} \]
Now that we have both the length (15 cm) and the width (10 cm) of the postcard, we can calculate the area: \[ \text{Area} = \text{Length} \times \text{Width} = 15 \text{ cm} \times 10 \text{ cm} = 150 \text{ square centimeters} \]
Therefore, the area of the postcard is 150 square centimeters.