The phrase “back of the envelope” comes from the fact that it’s often a quick, rough estimate of a complex problem. The idea is that you can quickly scribble down the calculations on the back of an envelope or napkin if need be, without having to take the time to spend time writing out the entire equation or working through a complicated set of formulas.

It originated in the mid-20th century, when people would take out their checkbook, write out the calculations on the back of it, and then use that rough estimate to decide if they should do something or not.

Today, the phrase is more often used to describe a quick and dirty estimate or calculation rather than a formal proof. The basic idea is that you can come up with a ballpark figure on the back of an envelope that is good enough to make a decision, without needing to delve into the specifics.

It is essentially a method of doing quick calculations that can save you time and effort, while still providing a good estimate of the desired outcome.

## Which part of the envelope is the back?

The back of an envelope is commonly referred to as the ‘flap’. The flap is the part of the envelope that is closed with either a gummed seal or a metal closure. Generally, there are two types of flaps: the classic triangle flap and the straight flap.

The triangle flap is triangular in shape, while the straight flap is rectangular and has two straight edges that meet at a point at the top of the envelope. On the back of the envelope, you will usually find text printed in the center which states “Do not bend” or “Return address.

” When addressing an envelope, the back flap is where you would typically write or print the return address and the address of the intended recipient.

## Does it matter which side of an envelope opening?

Yes, it does matter which side of an envelope opening you place the adhesive on. Using the wrong side could mean the letter won’t seal properly, the letter could get lost in transit, or your recipient may have trouble opening the envelope.

To prevent these problems, make sure you place the adhesive closure on the flap with the “This Side Up” arrow when sealing envelopes. This will help ensure that your letter is secure and the contents remain confidential.

## What is a back of the envelope analysis in real estate?

Back of the envelope analysis is a quick evaluation tool that real estate investors use to evaluate potential real estate investments. It is a simplified evaluation that involves calculating rough estimates of potential profitability and expenses associated with a rental property.

It is called a back of the envelope analysis because these calculations can typically be done on a single piece of paper. The goal of a back of the envelope analysis is to decide if a property is worthy of further consideration by providing a high-level overview of the investment.

Back of the envelope analyses focus on the core financial aspects of a rental property, such as the potential rental income, operating expenses, and cash flow. Investors use the estimate of these key metrics to gauge whether or not the property might be a beneficial investment.

The actual calculations involved with a back of the envelope analysis are generally based on inputs that are available with minimal research and data gathering. This includes information such as rent rates, real estate taxes, and estimated expenses.

Back of the envelope analysis is a useful tool for evaluating investment properties, as it can provide a good overview of potential profitability and risk in a short amount of time. It allows investors to quickly make decisions on whether to continue researching a property or move onto other potential investments.

Additionally, it provides a good starting point for further analysis of an investment property, such as conducting a more detailed cost-benefit analysis or financial modeling.

## What is napkin math?

Napkin math is a process of quick calculations to arrive at an approximate answer, usually while sketching out the problem on a napkin. This is commonly used in day-to-day conversations and can be used to get an idea of proportions or to estimate a budget, cost, or project timeline.

Napkin math can also be used to quickly come up with a proof, solve a problem, or arrive at a conclusion. Although napkin math doesn’t always get you to an exact answer, it’s a great way to get a ballpark figure or to get to an answer quickly.

Napkin math is a form of quick estimation that relies on the ability to identify patterns quickly and make approximations on-the-fly.