PSLE
Opal had two ribbons of the same length. She cut the first ribbon into equal parts of length 30 cm and to each part she tied 2 white paper cranes. After that, she cut the second ribbon into equal parts of length 40 cm and to each part she tied 4 purple paper cranes. When she finished tying, she counted that there were 12 more purple paper cranes than white paper cranes. How many paper cranes were there altogether?

	First ribbon	Second ribbon	Difference	Total
Length of each part	30 cm	40 cm
Number of balloons tied to each part	2 white balloons	4 purple balloons
LCM	120 cm	120 cm
Number of equal parts	120 ÷ 30 = 4	120 ÷ 40 = 3
Number of balloons for each ribbon per set	4 x 2 = 8	4 x 3 = 12	12 - 8 = 4	8 + 12 = 20

LCM of 30 and 40 = 120

Number of sets of 2 white paper cranes in a length of 120 cm
= 120 ÷ 30
= 4

Number of white paper cranes in a length of 120 cm
= 4 x 2
= 8

Number of sets of 4 purple paper cranes in a length of 120 cm
= 120 ÷ 40
= 3

Number of purple paper cranes in a length of 120 cm
= 3 x 4
= 12

Extra number of purple paper cranes in a length of 120 cm
= 12 - 8
= 4

Number of sets of paper cranes
= 12 ÷ 4
= 3

Total number of paper cranes in one set of 120 cm of white balloons and one set of 120 cm of purple balloons
= 8 + 12
= 20

Total number of paper cranes of the two ribbons
= 3 x 20
= 60

Answer(s): 60