In Singapore, every year around this time, folks who believe in hungry ghosts celebrate the one-month-long “Hungry Ghost Festival” (also known as the “Seventh Month”). The *Seventh* *Month* is like an Asian equivalent of Halloween, extended to one month—just spookier.

If you think that these spiritual vagabonds encircling the island are mere fictions or imaginations of some superstitious or irrational local folks who have put their blind faith in them, you’re in for a shock. These evil spirits can drive the hell out of ghosts agnostics, including those who deny the existence of such spiritual beings.

Hell money superstitious [or innumerate] folks can buy for a few bucks to pacify the “hungry ghosts.”

During the fearful *Seventh Month*, devotees would put on hold major life decisions, be it about getting married, purchasing a house, or signing a business deal. If you belong to the rational type, there’s no better time in Singapore to tie the knot (albeit there’s no guarantee that all your guests would show up on your D-Day); in fact, you can get the best deal of the year if your wedding day also happens to fall on a Friday 13—an “unlucky date” in an “unlucky month.”

**Problem solving in the ***Seventh Month*

I have no statistical data of the number of math teachers, who are hardcore *Seventh Month* disciples, who would play it safe, by going on some “mathematical fast” or diet during this fearful “inaupicious month.” As for the rest of us, let’s not allow fear, irrationality, or superstition to paralyze us from indulging into some creative mathematical problem solving.

Let’s see how the following “ghost” word problem may be solved using the *Stack Method*, a commonly used problem-solving strategy, slowing gaining popularity among math educators outside Singapore (which has often proved to be as good as, if not better than, the bar method in a number of problem-situations).

**During the annual one-month-long Hungry Ghost Festival, a devotee used 1/4 and $45 of the amount in his*** PayHell* account to buy an e-book entitled *That Place Called Hades*. He then donated 1/3 and $3 of the remaining amount to an on-line mortuary, whose members help to intercede for long-lost wicked souls. In the end, his *PayHell* account showed that he only had $55 left. How much money did he have at first?

Try solving this, using the Singapore model, or bar, method, before peeking at the quick-and-dirty stack-method solutions below.

From the stack drawing,

2 units = 55 + 13 + 15 + 15 = 98

4 units = 2 × 98 = 196

He had $196 in his* PayHell* account at first.

Alternatively, we may represent the stack drawing as follows:

From the model drawing,

2 units = 15 + 15 + 13 + 55 = 98

4 units = 2 × 98 = 196

The devotee had $196 in his account at first.

Another way of solving the “ghost question” is depicted below.

From the stack drawing,

6u = 55 + 13 + 15 + 15 = 98

12u = 2 × 98 = 196

He had $196 in his *PayHell* account at first.

**A ***prayerful exercise* for the lost souls

Let me end with a “wicked problem” I initially included in *Aha! Math*, a recreational math title I wrote for elementary math students. My challenge to you is to solve this rate question, using the Singapore bar method; better still, what about using the stack method? *Happy problem solving!*

How would you use the model, or bar, method to solve this “wicked problem”?

**Reference**

Yan, K. C. (2006). *Aha! math!* Singapore: SNP Panpac Education.

A businessman won this “lucky” urn with a $488,888 bid at a recent Hungry Ghost Festival auction.