In what proportion must water be mixed with honey so as to gain 10% by selling the mixture at the cost price of the honey? (Assume that water is freely available)

Let CP of honey be 1 per unit. To gain 10%, SP must be 1.1. Since water is free, the cost is only the honey. If we sell (1+x) units of mixture for 1.1, where 1 unit is honey and x is water, the cost is 1. So 1.1 = 1 + profit. This is not quite right. Let CP = 1. To gain 10%, we need to sell 1 unit of honey for 1.1. If we mix water, the volume becomes 1+x. Selling at cost price of honey means selling 1+x units for 1+x. If we want 10% profit, 1.1 * (Cost of 1 unit) = 1 * (Price of 1 unit). The ratio of water to honey is 1:10.