PSLE
Rachel had two ribbons of the same length. She cut the first ribbon into equal parts of length 80 cm and to each part she tied 2 pink paper cranes. After that, she cut the second ribbon into equal parts of length 100 cm and to each part she tied 5 silver paper cranes. When she finished tying, she counted that there were 20 more silver paper cranes than pink paper cranes. How many paper cranes were there altogether?

	First ribbon	Second ribbon	Difference	Total
Length of each part	80 cm	100 cm
Number of balloons tied to each part	2 pink balloons	5 silver balloons
LCM	400 cm	400 cm
Number of equal parts	400 ÷ 80 = 5	400 ÷ 100 = 4
Number of balloons for each ribbon per set	5 x 2 = 10	5 x 4 = 20	20 - 10 = 10	10 + 20 = 30

LCM of 80 and 100 = 400

Number of sets of 2 pink paper cranes in a length of 400 cm
= 400 ÷ 80
= 5

Number of pink paper cranes in a length of 400 cm
= 5 x 2
= 10

Number of sets of 5 silver paper cranes in a length of 400 cm
= 400 ÷ 100
= 4

Number of silver paper cranes in a length of 400 cm
= 4 x 5
= 20

Extra number of silver paper cranes in a length of 400 cm
= 20 - 10
= 10

Number of sets of paper cranes
= 20 ÷ 10
= 2

Total number of paper cranes in one set of 400 cm of pink balloons and one set of 400 cm of silver balloons
= 10 + 20
= 30

Total number of paper cranes of the two ribbons
= 2 x 30
= 60

Answer(s): 60