Hi Mhg,

Personally, I wouldn't bother trying to balance the whole thing, especially under time constraints.

Instead, I'd begin by considering the number of potassium atoms... I have 4 on the left of the equation and 2 on the right. To balance, the 4th number must be twice the 1st number... This means only C and D are viable.

I'd then move on to Iron. Given that there is only 1 iron atom on the left (as defined from the previous step), the same must be true on the right i.e. the fifth number must be 1, meaning that C is the only viable option.

This is more of a logic puzzle than chemistry!

Kind Regards

R