## Financial math: calculation of mortgage interest rate

Self-tutoring about financial math: the tutor mentions the mortgage interest rate. I was looking at the formula for the periodic payment of a mortgage: P=(-1(r/n))*L*(1+r/n)^(nt)/(1-(1+r/n)^(nt)) where P=payment r=rate n=payments per year (and compounding periods per year as well) t=years Specifically …

## Math: break-even year-over-year

Self-tutoring about math: the tutor mentions perhaps an oft-considered question. Suppose an investment loses x% this year. What percent does the resulting sum need to gain next year in order to break even? Imagine an investment of initial value \$250. …

## Math: increase then decrease by same percentage, or vice-versa

Tutoring math, you run into curiosities. The tutor mentions one with percentage. If an amount is increased, then decreased, by the same percentage, the net effect is shrinkage, regardless of which happens first. Let the amount be 100. Furthermore, for …

## Spreadsheets: Excel: finding the monthly loan payment

Tutoring financial math, spreadsheets might be used. The tutor shows how to find the monthly payment on a loan using Excel. In yesterday’s post I tell how to find the amount against the principal that a certain payment removes, using …

## Excel: payment against principal

Tutoring financial math, amortization arises. The tutor mentions the Excel function for it. Example: For a 25-year loan of \$100,000 at 4%, compounded monthly with monthly payments, what is the amount against the principal of the 101st payment? Solution: Using …

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## Financial math: what does amortization mean?

Tutoring math, definitions are needed. The tutor shares the definition of amortization. Amortization schedules and amortization functions are commonly encountered in financial math. What does amortization mean? amortization: the separation of a loan payment into two amounts: the payment against …

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## Math: what discount will exactly cancel the tax?

Tutoring high school math, you see financial word problems. The tutor gives an example. Problem: At 12% tax, what discount will lead to paying exactly the sticker price after tax? Solution The final price, f, is as follows: f = …

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## Calculator usage: finding final price after discount and tax with the HP-10B

Tutoring financial math, you might often use the HP-10B. The tutor shows how easily it can apply a discount then add tax to get the final price. Example: Imagine a handbag is regular price \$85 but is discounted by 20%. …

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## Calculator usage: markup on the HP-10B

Tutoring financial math, you might fall in love with a calculator. The tutor tells about markup on the HP-10B. Example: Imagine you buy a product for \$35, then want to apply a 25% markup. Find the tag price using the …

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## Calculator usage: memory on the HP-10B

Tutoring financial math, you’ll likely encounter the capable HP-10B. The tutor tells how to use its user-accessible memory. The HP-10B seems to have 11 dedicated places to store your own numbers. The locations are at 0 to 9, plus there …

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