Hi, i believe u r asking abt Qn 16 on Paper 2 right? I juz finished marking my girl's paper so here's the solution.

Qn : Ali, Bala, Clyde & Dingyi shared a box of pens. Ali rec'd 20% of the total no. of pens which Bala, Clyde & Dingyi rec'd altogether. Bala rec'd 50% of the total no. of pens which Ali, Clyde & Dingyi rec'd altogether. Clyde rec'd 80% of the total no. of pens which Ali, Bala & Dingyi rec'd altogether. Dingyi rec'd 6 pens. How many pens were in the box at first?

The solution is to use ratio method as follows:

A : BCD B : ACD C : ABD

20 : 100 50 : 100 80 : 100

1 : 5 (x3) 1 : 2 (x6) 4 : 5 (x2)

6 3 9 (total for each gp different)

Since LCM is 18, make each gp total into 18:

3 : 15 6 : 12 8 : 10 (total for each gp now 18)

A+B+C = 3+6+8 = 17

D = 18-17 = 1

Since D has 6 pens,

1 unit -> 6 pens

18 units -> 6 X 18 = 108 pens at first