Question
John has some black and grey balls. The total mass of all his balls is 230 g. He has 10 more grey balls than black balls. The average mass of the black balls is 10 g. The average mass of the grey balls is 12 g. How many balls does John have altogether?
3 m

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John has some black and grey balls. The total mass of all his balls is 230 g. He has 10 more grey balls than black balls. The average mass of the black balls is 10 g. The average mass of the grey balls is 12 g. How many balls does John have altogether?