PrepSwift Perecent Decrease Question

GRE Quant Problem Solving
1

Hi all! I recently did the “percent decrease” video + subsequent quiz on PrepSwift and got question #2 wrong. The question asks, “A shop is offering a 30% discount on the price of a certain item. If the shop wants to increase the price back to its original price, the discounted price should be increased by what percent?”

The way I did it was through choosing a suitable number, and so started off with the original number being 100. After accounting for the 30% discount, the “new” price would be 70. To go from 70 to 100, I calculated that it would be around a 143% increase, and that was my final answer. However, the Greg Mat solution is 43%. The answer key uses a different method than I used, and does make sense, but I was wondering if anyone could explain to me using the “pick a number” method. Because isn’t 100 greater than 70, therefore requiring it to go above 100% for 70 to go back to 100?

2

Hint: percent increase vs percent change.

3

I’m sorry, I don’t understand. I made the same mistake as above but I don’t really understand the hint. Percent change encompasses both percent increase and percent decrease, but how is that relevant here?

Thank you!

4

70 → 100 is not a case of “100 is 43% of 70” but “100 is 43% more than 70”.

1 Like
5

Can I ask why we get 143 when we use the “pick a number method”? How do I account for the 1 if that makes sense?

Thank you!