Question

A sample of clay was partially dried and was found to contain $50\%$ silica and $7$% water. The original clay contained $12\%$ water. The $\%$ of silica in the original sample is (the nearest integer) :

Answer 1

Silica Water Impurities
$\%$ in original clay a 12 (88-a)
$\%$ after partial drying 50 7 43
Clay on heating loses water only whereas percentage ratio of silica and impurities is not influenced. Therefore,
$\frac{a}{50}=\frac{88-a}{43};a=47.31$
So, answer is $47$.