Given
No.of green ribbon rolls used=4
No.of purple ribbon rolls used=8
Length of ribbon in one green roll=90 feet
Length of ribbon in one purple roll=60 feet
In order to find the difference in total green and purple ribbon used, we have to calculate the total length of the ribbons used.
Total length of green ribbon=Number of rolls*length of ribbon in one roll
=4*90
=360 feet
Total length of purple ribbon=number of rolls*length of ribbon in one roll
=8*60
=480 feet
The difference between the total length of green ribbon and purple ribbon=480-360
=120 feet ..