A farmer wants to buy a 10 kg bag of fertilizer (organic soil). They have the choice between two merchants. Merchant A sells the 10 kg bag for $10 and the bag indicates that the fertilizer is completely dry. Merchant B sells the 10 kg bag for 8$, and the bag indicates that the fertilizer has a water content of 20%. If the farmer can only use the solid constituents of the bag, which merchant has the better deal?

Since the farmer wants to buy a 10 kg bag of fertilizer, he should buy it from merchant A. However, Merchant A and B are selling at the same price for a unit value. In other words, Both Merchant A and B are selling 1kg of dry fertilizer for $1.

Explanation:

Which merchant has the better deal means which merchant offers the farmer a better deal.

For Merchant A,  10 kg bag = $10

meaning it contains a real 10 kg bag of dry fertilizer which the farmer can use without losing any Kg to drying.

While for Merchant B, 10 kg bag = $8

where the 10kg = 80% dry fertilizer + 20% water content

But the farmer can only use the solid constituents of the bag which means,

Merchant B is giving 80/100 x 10Kg of dry fertilizer for $8

That is, 8kg for $8

Since the farmer wants to buy a 10 kg bag of fertilizer, he should buy it from merchant A. However, Merchant A and B are selling at the same price for a unit value. In other words, Both Merchant A and B are selling 1kg of dry fertilizer for $1.