Calculators

article

Calculating the difference: a discussion of the use of calculators in the English primary classroom

Clare Green looks at the role of the calculator in the teaching and learning of primary mathematics.

article

Adding with the abacus

Nowadays the calculator is very familiar to many of us. What did people do to save time working out more difficult problems before the calculator existed?

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Mobile numbers

Age

5 to 11

Challenge level

In this investigation, you are challenged to make mobile phone numbers which are easy to remember. What happens if you make a sequence adding 2 each time?

problem

Secret number

Age

5 to 7

Challenge level

Annie and Ben are playing a game with a calculator. What was Annie's secret number?

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Clever keys

Age

7 to 11

Challenge level

On a calculator, make 15 by using only the 2 key and any of the four operations keys. How many ways can you find to do it?

problem

A conversation piece

Age

7 to 11

Challenge level

Take the number 6 469 693 230 and divide it by the first ten prime numbers and you'll find the most beautiful, most magic of all numbers. What is it?

problem

Reverse trick

Age

7 to 11

Challenge level

Tell your friends that you have a strange calculator that turns numbers backwards. What secret number do you have to enter to make 141 414 turn around?

game

Four go for two

Age

7 to 11

Challenge level

Four Go game for an adult and child. Will you be the first to have four numbers in a row on the number line?

problem

Exploring wild and wonderful number patterns

Age

7 to 11

Challenge level

EWWNP means Exploring Wild and Wonderful Number Patterns Created by Yourself! Investigate what happens if we create number patterns using some simple rules.

problem

It's all about 64

Age

7 to 11

Challenge level

Write the numbers up to 64 in an interesting way so that the shape they make at the end is interesting, different, more exciting ... than just a square.

problem

Forgot the numbers

Age

7 to 11

Challenge level

On my calculator I divided one whole number by another whole number and got the answer 3.125. If the numbers are both under 50, what are they?

problem

Number pattern explorations

Age

7 to 14

Challenge level

Investigate what happens if we create number patterns using some simple rules.

problem

Book codes

Age

7 to 11

Challenge level

Look on the back of any modern book and you will find an ISBN code. Take this code and calculate this sum in the way shown. Can you see what the answers always have in common?

problem

Special 24

Age

7 to 11

Challenge level

Find another number that is one short of a square number and when you double it and add 1, the result is also a square number.

problem

One million to seven

Age

7 to 11

Challenge level

Start by putting one million (1 000 000) into the display of your calculator. Can you reduce this to 7 using just the 7 key and add, subtract, multiply, divide and equals as many times as you like?

problem

Largest product

Age

11 to 14

Challenge level

Which set of numbers that add to 100 have the largest product?

problem

Round and round and round

Age

11 to 14

Challenge level

Where will the point stop after it has turned through 30 000 degrees? I took out my calculator and typed 30 000 ÷ 360. How did this help?

problem

Make a set of numbers that use all the digits from 1 to 9, once and once only. Add them up. The result is divisible by 9. Add each of the digits in the new number. What is their sum? Now try some other possibilities for yourself!

problem

Decimal time

Age

11 to 14

Challenge level

Use the clocks to investigate French decimal time in this problem. Can you see how this time system worked?

problem

Dating made easier

Age

14 to 16

Challenge level

If a sum invested gains 10% each year how long before it has doubled its value?

problem

Triangle incircle iteration

Age

14 to 16

Challenge level

Keep constructing triangles in the incircle of the previous triangle. What happens?

problem

Rain or shine

Age

16 to 18

Challenge level

Predict future weather using the probability that tomorrow is wet given today is wet and the probability that tomorrow is wet given that today is dry.

problem

Climbing powers

Age

16 to 18

Challenge level

$2\wedge 3\wedge 4$ could be $(2^3)^4$ or $2^{(3^4)}$. Does it make any difference? For both definitions, which is bigger: $r\wedge r\wedge r\wedge r\dots$ where the powers of $r$ go on for ever, or $(r^r)^r$, where $r$ is $\sqrt{2}$?

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Calculators

Calculating the difference: a discussion of the use of calculators in the English primary classroom

Adding with the abacus

Mobile numbers

Secret number

Clever keys

A conversation piece

Reverse trick

Four go for two

Exploring wild and wonderful number patterns

It's all about 64

Forgot the numbers

Number pattern explorations

Book codes

Special 24

One million to seven

Largest product

Round and round and round

Adding all nine

Decimal time

Dating made easier

Triangle incircle iteration

Rain or shine

Climbing powers