Hilda, Sarah and Kylie have equal number of erasers. Hilda packs all her erasers equally into 8 packets. Sarah packs all her erasers equally into 10 packets. Kylie packs all her erasers equally into 4 packets. 6 packets of Hilda's erasers, 5 packets of Sarah's erasers and 3 packets of Kylie's erasers add up to 720 erasers. How many erasers do they have altogether?

	Hilda	Sarah	Kylie
Number of packets	8	10	4
Number of erasers	40 u	40 u	40 u
Number of erasers in each packet	5 u	4 u	10 u

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

All the children have equal numbers of erasers. 
Make the number of erasers that each child has the same. LCM of 8, 10 and 4 = 40

Number of erasers that each child has = 40 u

Number of erasers in 1 packet of Hilda's erasers = 40 u ÷ 8 = 5 u
Number of erasers in 1 packet of Sarah's erasers = 40 u ÷ 10 = 4 u
Number of erasers in 1 packet of Kylie's erasers = 40 u ÷ 4 = 10 u

Number of erasers in 6 packets of Hilda's erasers, 5 packets of Sarah's erasers and 3 packets of Kylie's erasers
= (6 x 5 u) + (5 x 4 u) + (3 x 10 u)
= 30 u + 20 u + 30 u
= 80 u

80 u = 720

1 u = 720 ÷ 80 = 9

Total number of erasers that they have
= 3 x 40 u
= 120 u
= 120 x 9
= 1080

Answer(s): 1080