Question
PSLE
A box contained red balls and grey balls. 30% of the balls were grey. After some black balls were added to the box, 15% of the balls were grey. What percentage of the balls in the box were black?
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PSLE
A box contained red balls and grey balls. 30% of the balls were grey. After some black balls were added to the box, 15% of the balls were grey. What percentage of the balls in the box were black?