# Arithmetic Feedback

by Ron Kurtus

Readers have sent in a total of 19 comments and questions on Arithmetic issues. They are listed according to date.

## List of next 15 letters

### Country

Quotients that equal 4 to the negative 5 power General USA

Who named our numerals? Numbers Utah of USA

Formula for finding prime numbers Numbers USA

Don't understand how to reduce using prime numbers Numbers USA

Next 15 letters

First 15 letters

## Quotients that equal 4 to the negative 5 power

November 19, 2009

### Question

On my homework it says that I have to write THREE different quotients that equal 4 to the negative 5 power. I don't know ho to do it except for writing it one way only!:(

Tiffany - USA (18705)

4^-5 (4 to the negative 5 power) = 1/4^5 = 1/4*4*4*4*4 = 1/2^10 = 2^-10

I hope that is what your teacher is looking for.

## Who named our numerals?

February 27, 2009

### Question

Who named our numerals such as One (1), Two (2), Three (3), Four(4) - etc?
One can be spelled ONE or WON.
Two can be spelled TWO or TO or TOO.
Four can be spelled FOUR or FOR or FORE.
How far back into antiquity do these names go?

John Wilbur - Utah of USA (17338)

English words come from many sources and other languages. Thus, there are a number of words that sound the same but are spelled differently and have different meanings. They are called homophones or homonyms.

Besides the number examples, there are words like through and threw; rain, rein and reign.

## Formula for finding prime numbers

November 5, 2008

### Question

Regarding the statement that "there is no formula for finding prime numbers": It is not correct. There are at least two formulas. They are a bit unwieldy, I suppose, and thus not particularly useful for most people, but the formulas exist nonetheless.

I can say this quite certainly because my father wrote one of the formulas many years ago!

George - USA (16744)

Thanks for your feedback. You are correct. I updated the sentence to read: "there is no simple formula..."

## Don't understand how to reduce using prime numbers

February 2, 2008

### Question

I just don't understand how to reduce using prime numbers. What is the best way especially using large numbers and fractions? thank you

Yvette - USA (15263)

With a fraction, you are mainly concerned about reducing the denominator into prime factors.

Reducing any number into its prime factors is tedious. Usually, you try dividing the number by the small primes and then work your way up.

For example, supposed you have to find the prime factors of 140. Start trying dividing by 2: 140/2 = 70. Try again by 2: 70/2 = 35. You can see that you can't divide 35 by 2, so try dividing by 3. That doesn't work, so try dividing by the next prime, 5: 35/5 = 7. And 7 is a prime. Thus 140 = 2 X 2 X 5 X 7.

## Misc

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