PSLE
Ryan had 10 bags of beads. At first, each of the bags contained the same number of beads. He took 15 beads from each bag. After that, the total number of beads left in the 10 bags was equal to the total number of beads in 4 of the bags at first. What was the number of beads in each bag at first?

	4 bags at first	Total bags in the end
Number	4	10
Value	1 u + 15	1 u
Total value	4 u + 60	10 u

Number of beads in each bag in the end = 1 u
Number of beads in each bag at first = 1 u + 15

Number of beads in 4 bags at first 
= 4 x (1 u + 15)
= 4 u + 60

Total number of beads left in the 10 bags was equal to total number of beads in 4 bags at first.

10 u = 4 u + 60 
10 u - 4 u = 60
6 u = 60

1 u = 60 ÷ 6 = 10

Number of beads in each bag at first
= 1 u + 15
= 10 + 15
= 25

Answer(s): 25