Kylie had two rolls of ribbons of the same length but different designs. She cut the first roll of ribbon into equal pieces of length 42 cm and there were 4 squares on each piece of ribbon and cut the second roll of ribbon into equal pieces of length 70 cm and there were 7 triangles on each piece of ribbon as shown. After she finished cutting both rolls of ribbons, she counted that the total number of triangles was 16 more than the total number of squares. Find the length of one roll of ribbon in cm.
To make the lengths of the two rolls of ribbons were the same, find the LCM of 42 and 70.

LCM of 42 and 70 = 210

Number of sets of 42 cm in a length of 210 cm
= 210 ÷ 42
= 5

Number of sets of 70 cm in a length of 210 cm
= 210 ÷ 70
= 3

Number of squares in a length of 210 cm
= 5 x 4
= 20

Number of triangles in a length of 210 cm
= 3 x 7
= 21

Number of more triangles than squares in 1 set of 210 cm length
= 21 - 20
= 1

Number of sets of 1 more triangles than squares
= 16 ÷ 1
= 16

Length of one roll of ribbon
= 16 x 210
= 3360 cm

Answer(s): 3360 cm