# URGENT MATHS

I got 2 questions and I've been stuck on them for days and its due in 2 days.

1. For a quick way of doing multiplication, you can do:

for example: 81 x 89=? First you do 1x9=9 in which case you have to add '0' in front of it to make it 09. Then you add 1 to any of the 8s and multiply the tens digits making 72. You add the digits 72 to 09 making 7209.

Another one: 64x66=? 6x4= 24 and 6+1=7. Then I go 6x7=42. So the digits 42 and 24 makes 4224.

The question is WHEN can I do this. I already know that the last 2 digits must add up to 10, but what number does this method end? Over 100?

Second question. Why does 9+4=1? Because of clock arithmetic. 9o'clock + 4 hours= 1 o'clock, and the modulus is 12 for 12 hours for one cycle. I need to find out what other things uses a particular modulus. I've managed to think of a month(31,30,29,28) days.
What else?

Thanks heaps!

1. 👍
2. 👎
3. 👁

http://www.unc.edu/~rowlett/units/custom.html
16 ounces = 1 pint
2 pints = 1 quart
4 quarts = 1 gallon
etc.

inches, feet, yards, miles...

1. 👍
2. 👎
👤
Writeacher
2. Ok thanks. The problem is, I'm from Australia and we don't use those measurements. But I MIGHT be able to use other Australian measurements.

1. 👍
2. 👎
3. just keep on trying

1. 👍
2. 👎

## Similar Questions

1. ### math

you owe \$1,455.69 on a credit card at a 12.8% apr. you pay 15 days after the due date and the late fee is \$35.0, mkaing it 45 days of accrued interest. you pay \$250.00. how much is your balance after the payment. help, this is

2. ### Algebra

Two different radioactive isotopes decay to 10% of their respective original amounts. Isotope A does this is 33 days, while isotope B does this in 43 days. What is the approximate difference in the half-lives of the isotopes? 3

3. ### Math with science

Radioactive iodine treatment is so successful at treating hyperthyroidism that it has virtually replaced thyroid surgery. To the nearest full day, determine how long it will take for 400 millicuries of I-131, which has a half-life

4. ### Math

The table shows the relationship between the height of a tomato plant and the number of days since it has been planted. Days: 2,5,8,12,18,22,25,30,32,35 Height: 3,4,6,9,13,15,16,20,21,24 What does the y-intercept represent in this

1. ### Help Me On Math Please, If Anyone Is Available

A multiple choice test has 5 questions each with 5 possible answers. Find the probability of answering all the questions correctly. A. 1/3,125 B. 1/25 C. 1/625 D. 1/125 I'm on a test, and this is the only one I'm stuck on.

2. ### math

On a certain project, an employer lacked six days of working twice as many days as did his employee. If the sum of the days they worked is 42, how many days did each work?

3. ### Math

The Department manager recorded the number of sick days taken laster year by each employee, What is the mean number of days employees were sick? Round to the nearest hundredth. 2.86 days**** 2.57 days 2.43 days 2.29 days

4. ### Math

Ms. Carter recorded the number of sick days taken last year by each employee, as shown in the table. What is the mean number of days employees were sick? Round to the nearest hundredth A.3.63 days B.2 days C.3.22 days D.3 days

1. ### wlac

Kit borrowed \$15,500 at 11% ordinary interest for 120 days. After 70 days, she made a partial payment of \$3,000. What is the final amount due on the loan?

2. ### One more thing!

Day had broken cold and gray, exceedingly cold and gray, when the man turned aside from the main Yukon trail and climbed the high earth-bank, where a dim and little traveled trail led eastward through the fat spruce timberland. It

3. ### Math

Calculate the interest due on the following credit card balances: A. An unpaid balance of \$1629.53 at a rate of 19.50% for 21 days; and B. An unpaid balance of \$2639.99 at a rate of 22.95% for 30 days.

4. ### Stats

Richard has just been given a 4-question multiple-choice quiz in his history class. Each question has five answers, of which only one is correct. Since Richard has not attended class recently, he doesn't know any of the answers.