PSLE
Yen had two ribbons of the same length. She cut the first ribbon into equal parts of length 60 cm and to each part she tied 2 grey balloons. After that, she cut the second ribbon into equal parts of length 90 cm and to each part she tied 4 silver balloons. When she finished tying, she counted that there were 4 more silver balloons than grey balloons. How many balloons were there altogether?

	First ribbon	Second ribbon	Difference	Total
Length of each part	60 cm	90 cm
Number of balloons tied to each part	2 grey balloons	4 silver balloons
LCM	180 cm	180 cm
Number of equal parts	180 ÷ 60 = 3	180 ÷ 90 = 2
Number of balloons for each ribbon per set	3 x 2 = 6	4 x 2 = 8	8 - 6 = 2	6 + 8 = 14

LCM of 60 and 90 = 180

Number of sets of 2 grey balloons in a length of 180 cm
= 180 ÷ 60
= 3

Number of grey balloons in a length of 180 cm
= 3 x 2
= 6

Number of sets of 4 silver balloons in a length of 180 cm
= 180 ÷ 90
= 2

Number of silver balloons in a length of 180 cm
= 2 x 4
= 8

Extra number of silver balloons in a length of 180 cm
= 8 - 6
= 2

Number of sets of balloons
= 4 ÷ 2
= 2

Total number of balloons in one set of 180 cm of grey balloons and one set of 180 cm of silver balloons
= 6 + 8
= 14

Total number of balloons of the two ribbons
= 2 x 14
= 28

Answer(s): 28