It takes 3.075 seconds to download the entire webpage.
How to solve
Document size = 1KB = 1024B
Image size = 50KB = 51200B
Number of images = 7
Download rate = 1Mbps = 125000B/s
RTT = 100ms = 0.1s
Time to download document = Document size / Download rate = 1024B / 125000B/s = 0.008192s
Time to download each image = Image size / Download rate = 51200B / 125000B/s = 0.4096s
Total time to download images = Time to download each image * Number of images = 0.4096s * 7 = 2.8672s
Total download time = Time to download document + Total time to download images = 0.008192s + 2.8672s = 2.875392s
Total time with RTT = Total download time + 2 * RTT = 2.875392s + 2 * 0.1s = 3.075392s
Therefore, it takes 3.075 seconds to download the entire webpage.