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This problem trains for: SAT-I, AMC-8, GMAT.
Each of four kids wants to buy a beach ball. The first one is short of 18.9% of the cost. The second one is short of 49% of the cost. The third one would have money left over after the purchase equal to .22 of the cost. The fourth one would be short 13/25 of the cost. How many beach balls could they buy if they pooled their money?
Assume the cost of one ball is c. The first kid has:
where we have taken into account the fact that:
The second kid has:
The third kid has:
The fourth kid has:
where we have handled the conversion of the ratio 13/25 to a percentage, using the identity:
The total amount pooled buys b beach balls, where b is an integer. Therefore: