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Broad Topics > Numbers and the Number System > Place value

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One Million to Seven

Stage: 2 Challenge Level: Challenge Level:3 Challenge Level:3 Challenge Level:3

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?

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The Thousands Game

Stage: 2 Challenge Level: Challenge Level:1

Each child in Class 3 took four numbers out of the bag. Who had made the highest even number?

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Adding with the Abacus

Stage: 1, 2, 3 and 4

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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Path of Discovery Series 3: I Do and I Understand

Stage: 1

Marion Bond recommends that children should be allowed to use 'apparatus', so that they can physically handle the numbers involved in their calculations, for longer, or across a wider ability band,. . . .

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Number Sense Series: A Sense of 'ten' and Place Value

Stage: 1

Once a basic number sense has developed for numbers up to ten, a strong 'sense of ten' needs to be developed as a foundation for both place value and mental calculations.

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What a Joke

Stage: 4 Challenge Level: Challenge Level:2 Challenge Level:2

Each letter represents a different positive digit AHHAAH / JOKE = HA What are the values of each of the letters?

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Multiplication Magic

Stage: 4 Challenge Level: Challenge Level:1

Given any 3 digit number you can use the given digits and name another number which is divisible by 37 (e.g. given 628 you say 628371 is divisible by 37 because you know that 6+3 = 2+7 = 8+1 = 9). . . .

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Composite Notions

Stage: 4 Challenge Level: Challenge Level:3 Challenge Level:3 Challenge Level:3

A composite number is one that is neither prime nor 1. Show that 10201 is composite in any base.

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Arrange the Digits

Stage: 3 Challenge Level: Challenge Level:2 Challenge Level:2

Can you arrange the digits 1,2,3,4,5,6,7,8,9 into three 3-digit numbers such that their total is close to 1500?

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Even Up

Stage: 3 Challenge Level: Challenge Level:2 Challenge Level:2

Consider all of the five digit numbers which we can form using only the digits 2, 4, 6 and 8. If these numbers are arranged in ascending order, what is the 512th number?

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Phew I'm Factored

Stage: 4 Challenge Level: Challenge Level:3 Challenge Level:3 Challenge Level:3

Explore the factors of the numbers which are written as 10101 in different number bases. Prove that the numbers 10201, 11011 and 10101 are composite in any base.

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Three Times Seven

Stage: 3 Challenge Level: Challenge Level:3 Challenge Level:3 Challenge Level:3

A three digit number abc is always divisible by 7 when 2a+3b+c is divisible by 7. Why?

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Just Repeat

Stage: 3 Challenge Level: Challenge Level:3 Challenge Level:3 Challenge Level:3

Think of any three-digit number. Repeat the digits. The 6-digit number that you end up with is divisible by 91. Is this a coincidence?

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Which Is Quicker?

Stage: 2 Challenge Level: Challenge Level:1

Which is quicker, counting up to 30 in ones or counting up to 300 in tens? Why?

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An Alphanumeric

Stage: 5

Freddie Manners, of Packwood Haugh School in Shropshire solved an alphanumeric without using the extra information supplied and this article explains his reasoning.

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Learn about Number Bases

Stage: 3, 4 and 5

We are used to writing numbers in base ten, using 0, 1, 2, 3, 4, 5, 6, 7, 8, and 9. Eg. 75 means 7 tens and five units. This article explains how numbers can be written in any number base.

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Calculator Bingo

Stage: 2 Challenge Level: Challenge Level:2 Challenge Level:2

A game to be played against the computer, or in groups. Pick a 7-digit number. A random digit is generated. What must you subract to remove the digit from your number? the first to zero wins.

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Napier's Bones

Stage: 2 Challenge Level: Challenge Level:2 Challenge Level:2

The Scot, John Napier, invented these strips about 400 years ago to help calculate multiplication and division. Can you work out how to use Napier's bones to find the answer to these multiplications?

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Back to the Planet of Vuvv

Stage: 3 Challenge Level: Challenge Level:3 Challenge Level:3 Challenge Level:3

There are two forms of counting on Vuvv - Zios count in base 3 and Zepts count in base 7. One day four of these creatures, two Zios and two Zepts, sat on the summit of a hill to count the legs of. . . .

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Spell by Numbers

Stage: 2 Challenge Level: Challenge Level:2 Challenge Level:2

Can you substitute numbers for the letters in these sums?

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Eleven

Stage: 3 Challenge Level: Challenge Level:2 Challenge Level:2

Replace each letter with a digit to make this addition correct.

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What Number?

Stage: 1 Short Challenge Level: Challenge Level:2 Challenge Level:2

I am less than 25. My ones digit is twice my tens digit. My digits add up to an even number.

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Back to Basics

Stage: 4 Challenge Level: Challenge Level:3 Challenge Level:3 Challenge Level:3

Find b where 3723(base 10) = 123(base b).

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X Marks the Spot

Stage: 3 Challenge Level: Challenge Level:3 Challenge Level:3 Challenge Level:3

When the number x 1 x x x is multiplied by 417 this gives the answer 9 x x x 0 5 7. Find the missing digits, each of which is represented by an "x" .

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Really Mr. Bond

Stage: 4 Challenge Level: Challenge Level:3 Challenge Level:3 Challenge Level:3

115^2 = (110 x 120) + 25, that is 13225 895^2 = (890 x 900) + 25, that is 801025 Can you explain what is happening and generalise?

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Enriching Experience

Stage: 4 Challenge Level: Challenge Level:1

Find the five distinct digits N, R, I, C and H in the following nomogram

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Basically

Stage: 3 Challenge Level: Challenge Level:3 Challenge Level:3 Challenge Level:3

The number 3723(in base 10) is written as 123 in another base. What is that base?

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Tis Unique

Stage: 3 Challenge Level: Challenge Level:1

This addition sum uses all ten digits 0, 1, 2...9 exactly once. Find the sum and show that the one you give is the only possibility.

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Chocolate Maths

Stage: 3 Challenge Level: Challenge Level:1

Pick the number of times a week that you eat chocolate. This number must be more than one but less than ten. Multiply this number by 2. Add 5 (for Sunday). Multiply by 50... Can you explain why it. . . .

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Which Scripts?

Stage: 2 Challenge Level: Challenge Level:1

There are six numbers written in five different scripts. Can you sort out which is which?

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Cayley

Stage: 3 Challenge Level: Challenge Level:1

The letters in the following addition sum represent the digits 1 ... 9. If A=3 and D=2, what number is represented by "CAYLEY"?

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Oddly

Stage: 2 Challenge Level: Challenge Level:3 Challenge Level:3 Challenge Level:3

Find the sum of all three-digit numbers each of whose digits is odd.

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ABC

Stage: 2 Challenge Level: Challenge Level:3 Challenge Level:3 Challenge Level:3

In the multiplication calculation, some of the digits have been replaced by letters and others by asterisks. Can you reconstruct the original multiplication?

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Quick Times

Stage: 3 Challenge Level: Challenge Level:3 Challenge Level:3 Challenge Level:3

32 x 38 = 30 x 40 + 2 x 8; 34 x 36 = 30 x 40 + 4 x 6; 56 x 54 = 50 x 60 + 6 x 4; 73 x 77 = 70 x 80 + 3 x 7 Verify and generalise if possible.

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Never Prime

Stage: 4 Challenge Level: Challenge Level:2 Challenge Level:2

If a two digit number has its digits reversed and the smaller of the two numbers is subtracted from the larger, prove the difference can never be prime.

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Seven Up

Stage: 3 Challenge Level: Challenge Level:3 Challenge Level:3 Challenge Level:3

The number 27 is special because it is three times the sum of its digits 27 = 3 (2 + 7). Find some two digit numbers that are SEVEN times the sum of their digits (seven-up numbers)?

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Mini-max

Stage: 3 Challenge Level: Challenge Level:2 Challenge Level:2

Consider all two digit numbers (10, 11, . . . ,99). In writing down all these numbers, which digits occur least often, and which occur most often ? What about three digit numbers, four digit numbers. . . .

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Lesser Digits

Stage: 3 Challenge Level: Challenge Level:1

How many positive integers less than or equal to 4000 can be written down without using the digits 7, 8 or 9?

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Skeleton

Stage: 3 Challenge Level: Challenge Level:3 Challenge Level:3 Challenge Level:3

Amazing as it may seem the three fives remaining in the following `skeleton' are sufficient to reconstruct the entire long division sum.

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(w)holy Numbers

Stage: 2 Challenge Level: Challenge Level:3 Challenge Level:3 Challenge Level:3

A church hymn book contains 700 hymns. The numbers of the hymns are displayed by combining special small single-digit boards. What is the minimum number of small boards that is needed?

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Not a Polite Question

Stage: 3 Challenge Level: Challenge Level:2 Challenge Level:2

When asked how old she was, the teacher replied: My age in years is not prime but odd and when reversed and added to my age you have a perfect square...

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Cycle It

Stage: 3 Challenge Level: Challenge Level:2 Challenge Level:2

Carry out cyclic permutations of nine digit numbers containing the digits from 1 to 9 (until you get back to the first number). Prove that whatever number you choose, they will add to the same total.

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Permute It

Stage: 3 Challenge Level: Challenge Level:3 Challenge Level:3 Challenge Level:3

Take the numbers 1, 2, 3, 4 and 5 and imagine them written down in every possible order to give 5 digit numbers. Find the sum of the resulting numbers.

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Football Sum

Stage: 3 Challenge Level: Challenge Level:2 Challenge Level:2

Find the values of the nine letters in the sum: FOOT + BALL = GAME

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Digit Sum

Stage: 3 Challenge Level: Challenge Level:3 Challenge Level:3 Challenge Level:3

What is the sum of all the digits in all the integers from one to one million?

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Repeaters

Stage: 3 Challenge Level: Challenge Level:2 Challenge Level:2

Choose any 3 digits and make a 6 digit number by repeating the 3 digits in the same order (e.g. 594594). Explain why whatever digits you choose the number will always be divisible by 7, 11 and 13.

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Reverse to Order

Stage: 3 Challenge Level: Challenge Level:2 Challenge Level:2

Take any two digit number, for example 58. What do you have to do to reverse the order of the digits? Can you find a rule for reversing the order of digits for any two digit number?

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Latin Numbers

Stage: 4 Challenge Level: Challenge Level:1

Let N be a six digit number with distinct digits. Find the number N given that the numbers N, 2N, 3N, 4N, 5N, 6N, when written underneath each other, form a latin square (that is each row and each. . . .

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Basic Rhythms

Stage: 5 Challenge Level: Challenge Level:2 Challenge Level:2

Explore a number pattern which has the same symmetries in different bases.

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Binary Squares

Stage: 5 Challenge Level: Challenge Level:2 Challenge Level:2

If a number N is expressed in binary by using only 'ones,' what can you say about its square (in binary)?