1. ## ferterliser in paddock problem

A farmer needs to spread fertiliser over a paddock measuring 40 m by 80 m. The instructions on the fertiliser bag say to use 80 grams per square metre. How many kilograms of fertiliser will be needed?

I did 80 divied by 1000 = 0.08 kg is that right?

2. All you did was convert 80 g to kg. But 0.08 kg of fertilizer is supposed to be used for 1 square meter. But the paddock is not 1 square meter, is it? How do we find out the area of this paddock?

3. would it be 40m x 80m = 3200/ 1000 = 3.2 kg

4. No, that's not right. You got the area, $\displaystyle 3200\,\text{m}^2$. Why on earth would you try to convert to kg by dividing by 1000? Can't do that, my friend.

We have a proportion here. If 0.08 kg is used for $\displaystyle 1\,\text{m}^2$, how many kilograms is used for $\displaystyle 3200\,\text{m}^2$? You could set up the proportion like this:
$\displaystyle \dfrac{0.08}{1} = \dfrac{x}{3200}$
... and solve for x.

5. would 0.08 x 3200 = 256 kg for 3200 be correct

6. Yes, it is 256 kg.