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After —
Daniel : 9 units
Alex : 3 units

At first —
Daniel : 10 units
Alex : 2 units

10 units – 2 units = 8 units = 160
1 unit = 20
9 units + 3 units = 12 units = 12 x 20 = 240

Ans : $240.

 

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at beginning, Daniel has 10u
after Daniel give Alex 1 u,
now, Daniel has 9u, and Alex has 3 u ( Daniel has 3 times more than Alex)
so at the beginning, Alex has 2u, so 10u – 2u = 160, 1u is 20

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D-A=160

A = D-160

(9/10)D = 3(A+[1/10]D)

(9/10)D = 3([D-160]+[1/10]D)

(9/10)D = 3D – 480 + [3/10] D

480 = 12/5 D

D = 200

A = 200-160 = 40

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1)  d = a + 160

2) 0.9d = (a + 0.1d) * 3

d = 5a

4a = 160

a = 40

d =200

 

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Before :
Daniel : 10 units + $160
Alex : 10 units

After :
Daniel : 3 parts
Alex : 1 part

Since Daniel gives 1/10 to Alex, he has given (1 unit + $16) to Alex

In the “After” model,

1 part (for Alex) = 11 units + $16
3 parts (for Daniel) = 9 units + $144 ; ie. 1 part for Daniel is 3 units + $48

The difference is 2 parts : this is the key

2(11units + 16) = 6 units + $96
22 units + $32 = 6 units + $96
16 units = $64
1 unit = $4

At first,
Alex has 10 units = 10 X $4 = $40
Daniel has 10 units + $160 = $40 + $160 = $200.

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Not sure how to draw model here. Need to have before and after model.

Before :
Daniel : 10 units + $160
Alex : 10 units

After :
Daniel : 3 parts
Alex : 1 part

Since Daniel gives 1/10 to Alex, he has given (1 unit + $16) to Alex

In the “After” model,

1 part (for Alex) = 11 units + $16
3 parts (for Daniel) = 9 units + $144 ; ie. 1 part for Daniel is 3 units + $48

The difference is 2 parts : this is the key

2(11units + 16) = 6 units + $96
22 units + $32 = 6 units + $96
16 units = $64
1 unit = $4

At first,
Alex has 10 units = 10 X $4 = $40
Daniel has 10 units + $160 = $40 + $160 = $200.

Ref: http://www.kiasuparents.com/kiasu/forum/viewtopic.php?p=1814#p1814

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