PSLE
Usha had two strings of the same length. She cut the first string into equal parts of length 50 cm and to each part she tied 2 yellow balls. After that, she cut the second string into equal parts of length 60 cm and to each part she tied 3 brown balls. When she finished tying, she counted that there were 12 more brown balls than yellow balls. How many balls were there altogether?

	First string	Second string	Difference	Total
Length of each part	50 cm	60 cm
Number of balloons tied to each part	2 yellow balloons	3 brown balloons
LCM	300 cm	300 cm
Number of equal parts	300 ÷ 50 = 6	300 ÷ 60 = 5
Number of balloons for each string per set	6 x 2 = 12	3 x 5 = 15	15 - 12 = 3	12 + 15 = 27

LCM of 50 and 60 = 300

Number of sets of 2 yellow balls in a length of 300 cm
= 300 ÷ 50
= 6

Number of yellow balls in a length of 300 cm
= 6 x 2
= 12

Number of sets of 3 brown balls in a length of 300 cm
= 300 ÷ 60
= 5

Number of brown balls in a length of 300 cm
= 5 x 3
= 15

Extra number of brown balls in a length of 300 cm
= 15 - 12
= 3

Number of sets of balls
= 12 ÷ 3
= 4

Total number of balls in one set of 300 cm of yellow balloons and one set of 300 cm of brown balloons
= 12 + 15
= 27

Total number of balls of the two strings
= 4 x 27
= 108

Answer(s): 108