Ivory, Zoe and Betty have equal number of stickers. Ivory packs all her stickers equally into 5 packets. Zoe packs all her stickers equally into 3 packets. Betty packs all her stickers equally into 10 packets. 4 packets of Ivory's stickers, 2 packets of Zoe's stickers and 6 packets of Betty's stickers add up to 620 stickers. How many stickers do they have altogether?

	Ivory	Zoe	Betty
Number of packets	5	3	10
Number of stickers	30 u	30 u	30 u
Number of stickers in each packet	6 u	10 u	3 u

All the stickers can be put into the packets without remainder.

All the children have equal numbers of stickers. 
Make the number of stickers that each child has the same. LCM of 5, 3 and 10 = 30

Number of stickers that each child has = 30 u

Number of stickers in 1 packet of Ivory's stickers = 30 u ÷ 5 = 6 u
Number of stickers in 1 packet of Zoe's stickers = 30 u ÷ 3 = 10 u
Number of stickers in 1 packet of Betty's stickers = 30 u ÷ 10 = 3 u

Number of stickers in 4 packets of Ivory's stickers, 2 packets of Zoe's stickers and 6 packets of Betty's stickers
= (4 x 6 u) + (2 x 10 u) + (6 x 3 u)
= 24 u + 20 u + 18 u
= 62 u

62 u = 620

1 u = 620 ÷ 62 = 10

Total number of stickers that they have
= 3 x 30 u
= 90 u
= 90 x 10
= 900

Answer(s): 900