**Just where is that calculator when you need it? This week, Education World tells you where to find a variety of helpful on-line math tools. Find calculators and flashcards plus tools for converting kilometers to miles, Roman numerals to Arabic, and fractions to decimals. Included: Simple activities to help you use these on-line math tools!**

Do your students think that math can't be done without a calculator? Have they forgotten how to convert Fahrenheit to Celsius? No matter what they do or don't remember, students will find this collection of on-line math tools both enlightening and useful. Encourage your students to trace the history of the calculator, to figure the area of a cube, to find the day's Celsius temperature, to work a slide rule -- or invite them to try some of the activities we've provided. (Answers are included!)

Calculators are probably the math tools most familiar to your students. Do they know people have used calculating machines for more than 100 years? Students may be surprised to discover that today's machines have a lot more in common with the original machines than they think. Would they believe that an 1885 adding machine could still be useful? Show them!

Encourage students to read about the history of Calculating Machines and then have them use the 1885 Felt &Tarrant "Comptometer" adding machine to answer the following questions.

What number is...

- 4 tens, 2 ones, 6 tenths, and 1 hundredth?
*(42.61)* - 1 hundred-thousands, 3 ten-thousands, 4 thousands, 5 hundreds, 6 tens, 7 ones, 8 tenths, and 2 hundredths?
*(134,567.82)* - 3 thousands, 5 hundreds, 6 tens, 1 one, 4 tenths, 5 hundredths + 1 thousand, 4 hundreds, 1 ten, 6 ones, 4 tenths, 5 hundredths?
*(4 thousands, 9 hundreds, 7 tens, 7 ones, 9 tenths, and 0 hundredths, or 4977.90)* - 23,487.77 + 67,890.68?
*(91,378.45)* - $145,789.50 + $252,110.47?
*($397,899.97)*

Of course, today's calculators do more than add, subtract, multiply, and divide. Some can help save the environment -- or make you a millionaire.

Ask students to use the Basic JavaScript Calculator and the information at Louisiana Public Broadcasting's Forest Web sites to answer one or both of these questions: (Answers will vary.)

Then invite students to use the Kids Bank.com **Millionaire Calculator** or **Car Calculator** to find the answers to these questions:

- Mr. Benton is 25 years old. When he retires in 40 years, he wants to have 1 million dollars in his savings account. Mr. Benton's bank pays an interest rate of 5% on savings accounts. How many years will it take Mr. Benton to become a millionaire if he puts $50 into a savings account and adds another $50 every week?
*(61 years)*At 5% interest, how much money will Mr. Benton have to save each week to become a millionaire in 40 years? Try different numbers in the How Much Will You Save Each Week? box until you find the correct answer.*($150)*If Mr. Benton can save only $100 a week, what interest rate will he have to earn to become a millionaire in 40 years? Try different numbers in the What's the Interest Rate? box until you find the correct answer.*(about 7%)* - Julie is 10 years old. She wants to buy her own car when she turns 16. Julie's bank pays an interest rate of 6% on savings accounts. How much money will Julie accumulate if she puts $10 into a savings account and saves $10 a week for the next 6 years?
*($5471.42)*Julie thinks she'll be able to buy the kind of used car she wants for about $8,000. How much money will she have to save each week to have enough money to buy an $8,000 car? Try different numbers in the How Much Will You Save Each Week? box until you find the correct answer.*(about $15)*

Encourage students to find the pattern in each of these Calculator Pattern Puzzles. Then invite them to use a calculator to calculate the missing numbers.

- 5, 10, ___, 40, ___, 160.
*(20, 80: doubles the previous number.)* - 1, 4, 7, ___, 13, 16, ___, 22.
*(10, 19: add 3 to the previous number.)* - 7, 14, ___, ___, 35, 42, ___.
*(21, 28, 49: add 7.)* - 40, 34, 28, ___, 16, 10, ___, -2.
*(22, 4: subtract 6.)* - 1, 1, 2, 4, 3, ___, ___, 16, 5, ___.
*(9, 4, 25: each number followed by the number squared.)*

When students have completed the puzzles, ask them to create their own pattern puzzles and challenge their classmates to solve them.

Encourage students to Convert It! and then solve these problems:

- Next weekend, Bill is running in a 5-kilometer race. As part of his training program, he wants to run 5 kilometers every day this week. How many miles will Bill run in the next seven days?
*(Five kilometers is 3.107 mi., so Bill will run 21.749mi.)* - Your class is having a graduation party, and you're in charge of providing the drinks. There are 20 students in your class, and you estimate that each student will drink two 8-oz. cups of juice. The juice you want is sold only in 2-liter bottles. How many bottles should you buy?
*(Each student will drink 16 oz. of juice, for a total of 320 oz. or 10 quarts. Ten quarts is 9.464 liters. You'll need five 2-liter bottles.)* - Next week, Libby is traveling to France. She knows that the temperature there will be about 25 degrees Celsius. Should Libby pack her shorts or her mittens?
*(Her shorts. 25 degrees Celsius is 77 degrees Fahrenheit.)*

- MDCCCX
*(1810)* - MMV
*(2005)* - MDCX
*(1610)* - MDII
*(1502)* - MMDX
*(2510)* - MCMXCIX
*(1999)*

Ask students to locate and use the correct reference at Dave's Math Tables to find

- the decimal equivalent of 3/7
*(0.428571)* - the area of a parallelogram, if b is 10 feet and h is 13 feet
*(bxh or 130 feet)* - definitions of
and**circumference, diameter,****radius**

(circumference: the distance around the circle; diameter: the longest distance from one end of a circle to the other; radius: the distance from center of circle to any point on it) - the number of 0s in one quintillion
*(18)* - the value of
*pi*

(3.141592)

Provide students with steps 1 through 10 of the problem It's Going, Going at **PBS Teacher Source** and have them use the Function Grapher to find the answer. *(He wins the game!)*

For more information about on-line tools, both old and new, check out these...

- The Abacus contains information about the abacus and includes a working abacus.
- The Numeroscope This "multi-media, interactive laboratory for exploring the number systems which form the basis for today's cryptography" can be used to perform a number of mathematical calculations.
- Use of the Slide Rule as a Teaching Tool contains information about the history and use of the slide rule.
- Martindale's Calculators On-Line Center provides links to more than 8,000 on-line calculators.
- Measurement Formulas includes
**General Formulas, Perimeter Formulas, Area Formulas,**and**Volume Formulas.**

- Flashcards for Kids Elementary students can choose Type of Math, Complexity, and Number Size and practice, practice, practice.
- Java Flashcards and Non-Java Flashcards Students can practice almost any kind of math activity at either of these sites.

Article by Linda Starr

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