Kenny took 3 hours to paint 3 bedrooms. He took the same amount of time to paint the first 2 bedrooms. He took 15 minutes longer to paint the third bedroom than the first. How many minutes did he take to paint the third bedroom?

1. Convert the total time taken into minutes.

$3 \text{ hours} = 3 \times 60 = 180 \text{ minutes}$

2. Find the total time if all three bedrooms took the same time as the first bedroom.

Since the third bedroom took $15$ minutes longer, we subtract this extra time from the total:
$180 - 15 = 165 \text{ minutes}$

3. Calculate the time taken for the first bedroom (1 unit).

$165 \div 3 = 55 \text{ minutes}$

4. Calculate the time taken for the third bedroom.

$55 + 15 = 70 \text{ minutes}$