Siew Yan had some red coloured beads and yellow coloured bead. The number of red coloured beads was 4/9 as many as the number of yellow coloured beads. After giving away 21 yellow beads, Siew Yan 2/3 as many red coloured beads as yellow coloured beads. How many red beads did siew yan have?
r = 4/9 y
r = 2/3 (y-21)
4/9 y = 2/3 (y-21)
4/9 y = 2/3 y - 14
2/9 y = 14
y = 63
r = 28
check:
63-21 = 42.
28 = 2/3 of 42