If a quantity increases by 25% and then decreases by 25%, will the resultb e the original quatity?

You actually won't get the same answer Becuz when you increase 25% to a number. and the decrease 25% from that number you won't get the original amount. since your not decreases. 25 from the original number

No the result will not be the original quantity, it will be less than the original.

Example: 100 increased by 25% becomes 125. 125 decreased by 25% becomes 93.75. This holds true for any number.

This is because you are taking 25% of the marked up number and not the original number.