**Andrea has $200 more than Bala. Andrea gives 60% of his money to Bala. Bala then gives 25% of his money to Andrea. In the end, Bala has $200 more than Andrea. How much did Andrea have at first?** (Nanyang Prelim 2006 Q48)

At first -----

Andrea ----- 1 unit + 200

Bala ----- 1 unit

Andrea gives 60% -----

Andrea ----- 1 unit + 200 – 0.6 unit – 120

Bala ----- 1 unit + 0.6 unit + 120

Andrea ----- 0.4 unit + 80

Bala ----- 1.6 units + 120

Bala gives 25% -----

Bala ----- 1.6 units + 120 – 0.4 unit – 30

Andrea ----- 0.4 unit + 80 + 0.4 unit + 30

Bala ----- 1.2 units + 90

Andrea ----- 0.8 unit + 110

Bala now has $200 more -----

Bala – Andrea ----- 200

1.2 units + 90 – 0.8 unit –110 ----- 200

0.4 unit – 20 ---- 200

0.4 unit ----- 200 + 20 = 220

1 unit ---- 220 divided by 0.4 = 550

Andrea at first -----

1 unit + 200 ----- 550 + 200 = 750**Answer: Andrea had $750 at first.**

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## Thursday, October 02, 2008

### PSLE Math Q on ratio

Labels:
Mathematics,
Ratio

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## 3 comments:

Hi Teacher,

There seems to have a confusion here.

Andrea has $200 more than Bala. Andrea gives 60% of his money to Bala. Bala then gives 25% of his money to Andrea. In the end, Bala has $200 more than Andrea. How much did Andrea have at first?

How did you derive the 120?

The question above stated that Andrea gives 60% of his money....

But how come you use the 60% * 200?

This part is quite confuse...Are you using assumption?

Another confusing part is when you minus 0.6 units,,,

I am totally clueless....

Andrea had 1 unit + 200 at first.

If Andrea gives 60%, then ….

1 unit x 60% = 0.6 unit

200 x 60% = 120

Therefore Andrea gave away 0.6 unit and 120, which means….

What Andrea had at first – What Andrea gave -----

1 unit + 200 – 0.6 unit - 120

Thanks Teacher....I get picture,,,

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