PSLE
Gem had two streamers of the same length. She cut the first streamer into equal parts of length 40 cm and to each part she tied 2 black stars. After that, she cut the second streamer into equal parts of length 50 cm and to each part she tied 5 purple stars. When she finished tying, she counted that there were 30 more purple stars than black stars. How many stars were there altogether?

	First streamer	Second streamer	Difference	Total
Length of each part	40 cm	50 cm
Number of balloons tied to each part	2 black balloons	5 purple balloons
LCM	200 cm	200 cm
Number of equal parts	200 ÷ 40 = 5	200 ÷ 50 = 4
Number of balloons for each streamer per set	5 x 2 = 10	5 x 4 = 20	20 - 10 = 10	10 + 20 = 30

LCM of 40 and 50 = 200

Number of sets of 2 black stars in a length of 200 cm
= 200 ÷ 40
= 5

Number of black stars in a length of 200 cm
= 5 x 2
= 10

Number of sets of 5 purple stars in a length of 200 cm
= 200 ÷ 50
= 4

Number of purple stars in a length of 200 cm
= 4 x 5
= 20

Extra number of purple stars in a length of 200 cm
= 20 - 10
= 10

Number of sets of stars
= 30 ÷ 10
= 3

Total number of stars in one set of 200 cm of black balloons and one set of 200 cm of purple balloons
= 10 + 20
= 30

Total number of stars of the two streamers
= 3 x 30
= 90

Answer(s): 90