36% of the contents of a tin of sweets have been eaten. Today, 25% of the remaining sweets will be eaten. The same number of sweets will be eaten on each of the following 2 days.

What % of its original contents will it then contain?

Determine what they are trying to ask, and what you will need to solve it

Eliminate any non-essential information

Draw a picture, graph, or equation

In moments of high stress like exam taking, always work with the paper they give you to avoid careless mistakes.

Solve.

For simplicity, let’s say we originally start with 100 sweets in the tin. If we have 36% of 100 sweets eaten (100-36 = 64) , then 64 would be leftover. Now we need to take 25% of the remaining sweets, so we will need to take (64)(0.25) = (64)/(4) = 16. So if 25% of 64 sweets are taken, then we are left with 64-16 = 48 left. Note that it says the same NUMBER are taken the next two days, not PERCENT, so we are using 16 sweets instead of 25% of the remaining total.

Over the next two days: 48-16-16 = 48 - 32 = 16

So we are left with 16 sweets. But wait, didn’t we want to find the percentage of how many were left from the original day? We just need to say 16%, because we started with 100 sweets which were to represent 100%.

Using calculation tricks like this, albeit simple, can really help simplify the problem and make it much easier to do mentally. What do you prefer? Taking 25% of 64% or taking 25% aka ¼ of 64 candies. Perspective is everything.

\fcolorbox{red}{grey!30}{Therefore the answer is C, $16$%}