Mellody's Math: How Much to Invest?

N E W   Y O R K, Nov. 12 -- Each week, financial expert Mellody Hobson answers your questions about personal finance.

The average woman receives $4,200 annually in pension benefits, vs. $7,800 annually for men.

The only way to answer your question is to think through your own personal goals. Specifically, you need to try to estimate how much you will need when you retire. To do so, you must consider what lifestyle goals you will have — if you plan to retire to a retirement community somewhere else or to your home.

Do you plan on working, getting a second job, or starting a business? Do you plan to travel? All of those things must be considered. It's an extensive process to think through.

A couple of rules: First, we are living longer so you need to plan accordingly. The average woman will outlive her husband by seven years.

Second, typically you need less in your retirement than in your current life because you are likely to have paid off major expenses like a home or children's college, by that time. We are planning on doing a segment in the future on how much money you need to retire so stay tuned!