Yen used a total of 8 blue ribbons and black ribbons. Each blue ribbon was 4 m long. Each black ribbon was 5 m long. The total length of ribbons she used was 34 m. How many black ribbons did she use?
If all the ribbons are blue,
total length of ribbons
= 8 x 5
= 40 m
Difference between the length of 1 blue ribbon and 1 black ribbon
= 5 - 4
= 1
Difference between the length of all the blue ribbons and all the black ribbons
= 40 - 34
= 6 m
Number of blue ribbons
= 6 ÷ 1
= 6
Number of black ribbons
= 8 - 6
= 2
Answer(s): 2
