Paul creates a CD by mixing together
songs that are either 3 minutes or
4 minutes long. His CD has 22 songs
and is 78 minutes long. How many
three-minute and how many four-minute
songs did he use?

Paul created 10 three minutes songs and 12 four minutes songs.

Step-by-step explanation:

The song he created on his CD is either 3 minutes long or 4 minutes long.

His CD has 22 songs and is 78 minutes. The number of 3 minutes and 4 minutes song can be calculated below.

Let

a = number of 3 minutes song

b = number of 4 minutes song

number of song = 22

a + b = 22(i)

3a + 4b = 78(ii)

Make a subject of the formula in equation (i)

a = 22 - b

Insert the value of a in equation (ii)

3(22 - b) + 4b = 78

66 - 3b + 4b = 78

b = 78 - 66

b = 12

insert the value of b in equation (i)

a + b = 22

a + 12 = 22

a = 22 - 12

a = 10

Paul created 10 three minutes songs and 12 four minutes songs.

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step-by-step explanation: