Question

philip is downloading applications (apps) and songs to his tablet. he downloads 7 apps and 6 songs. each song takes an average of 0.8 minutes longer to download than each app. if it takes 21.7 minutes for his downloads to finish, which of the following systems could be used to approximate a, the average number of minutes it takes to download one app, and s, the average number of minutes it takes to download one song? choose 1 answer: (a) a + s = 21.7 6s = 7a - 0.8 (b) a + s = 21.7 7a = 6s - 0.8 (c) 7a + 6s = 21.7 s = a - 0.8 (d) 7a + 6s = 21.7 a = s - 0.8

Explanation:

Step1: Set up time - total equation

The total time for downloads is the sum of the time to download apps and the time to download songs. He downloads 7 apps, with each app taking $a$ minutes, and 6 songs, with each song taking $s$ minutes. The total time is 21.7 minutes. So, the first - equation is $7a + 6s=21.7$.

Step2: Set up time - difference equation

Each song takes an average of 0.8 minutes longer to download than each app. So, $s=a + 0.8$ (which can also be written as $a=s - 0.8$).

Answer:

D. $7a + 6s = 21.7$, $a=s - 0.8$