Answer: 60% or 0.6
Explanation:
A discount simply means the amount that is deducted from the normal cost of a good or service.
In the question above, the store was offering 40% as discount, this means that he'll only pay 60% of the price of the good. Note that (100% - 40% = 60%).
Therefore, the number that he should multiply the prices on the tags by to find the price he would have to pay will be 60% = 0.6.