Hi Eric, thanks for the answer. I don't understand the first part though, on why it is 400><

y starts out as “its own value” of 100%.

(Starting values are always assigned to be 100%, so if let’s say you start out having $500, then $500 represents 100% of your money)

At the end, y is to be increased “BY 300%”, not “TO 300%”. This means that 100% is being increased to 400%, since there is an increase in percentage points by 300%.

Hence, the final value of y is 4 times the starting value of y. We will need to use this to solve the question for the change in x.

Is it like model method, where y is one box, then 300% is like saying, increase by 3 times?

In this case you are not given any value whatsoever for y and x, so this question becomes rather challenging and we have no choice but to express the answer as such.

These type of questions are very hard to understand and I believe that a large proportion of all students will get stuck at such questions.

Yes! You got it.

y is like 1 unit.

An increase in 300% means an increase in 3 units.

So the final will be 400%, or 4 units.

You start out with $10. That’s 100% at the start.

If your money increases by 100%, it means your money has increased by $10, for a new sum of $20.

If instead your money increases by 500%, it means your money has increased by $50, for a new sum of $60.

Thank you!:D

An alternative phrasing of such questions is

Find the percentage decrease in x if the value of y is quadrupled.

Sometimes they will mention the numerical number to multiply, rather than a percentage number to multiply.

Thank you!