Other tags that relate to Which Numbers? (1)
Divisibility. Working systematically. Multiplication & division. Selecting and using information. Factors and multiples. Addition & subtraction. Prime numbers. Generalising. Making and testing hypotheses. Odd and even numbers.There are 342 results
Broad Topics > Thinking Mathematically > Working systematically
Star Product Sudoku
Age 11 to 16
Challenge Level
The puzzle can be solved by finding the values of the unknown digits (all indicated by asterisks) in the squares of the $9\times9$ grid.
American Billions
Age 11 to 14
Challenge Level
Play the divisibility game to create numbers in which the first two digits make a number divisible by 2, the first three digits make a number divisible by 3...
Integrated Product Sudoku
Age 11 to 16
Challenge Level
This Sudoku puzzle can be solved with the help of small clue-numbers on the border lines between pairs of neighbouring squares of the grid.
Product Sudoku
Age 11 to 16
Challenge Level
The clues for this Sudoku are the product of the numbers in adjacent squares.
Curious Number
Age 7 to 11
Challenge Level
Can you order the digits from 1-3 to make a number which is divisible by 3 so when the last digit is removed it becomes a 2-figure number divisible by 2, and so on?
How Old Are the Children?
Age 11 to 14
Challenge Level
A student in a maths class was trying to get some information from her teacher. She was given some clues and then the teacher ended by saying, "Well, how old are they?"
Ones Only
Age 11 to 14
Challenge Level
Find the smallest whole number which, when mutiplied by 7, gives a product consisting entirely of ones.
Ben's Game
Age 11 to 16
Challenge Level
Ben, Jack and Emma passed counters to each other and ended with the same number of counters. How many did they start with?
Multiples Sudoku
Age 11 to 14
Challenge Level
Each clue in this Sudoku is the product of the two numbers in adjacent cells.
A First Product Sudoku
Age 11 to 14
Challenge Level
Given the products of adjacent cells, can you complete this Sudoku?
Shopping Basket
Age 11 to 16
Challenge Level
The items in the shopping basket add and multiply to give the same amount. What could their prices be?
Two Primes Make One Square
Age 7 to 11
Challenge Level
Can you make square numbers by adding two prime numbers together?
Seven Pots of Plants
Age 7 to 11
Challenge Level
There are seven pots of plants in a greenhouse. They have lost their labels. Perhaps you can help re-label them.
Penta Primes
Age 7 to 11
Challenge Level
Using all ten cards from 0 to 9, rearrange them to make five prime numbers. Can you find any other ways of doing it?
Magic Vs
Age 7 to 11
Challenge Level
Can you put the numbers 1-5 in the V shape so that both 'arms' have the same total?
A Mixed-up Clock
Age 7 to 11
Challenge Level
There is a clock-face where the numbers have become all mixed up. Can you find out where all the numbers have got to from these ten statements?
Twin Corresponding Sudoku III
Age 11 to 16
Challenge Level
Two sudokus in one. Challenge yourself to make the necessary connections.
Multiplication Squares
Age 7 to 11
Challenge Level
Can you work out the arrangement of the digits in the square so that the given products are correct? The numbers 1 - 9 may be used once and once only.
Integrated Sums Sudoku
Age 11 to 16
Challenge Level
The puzzle can be solved with the help of small clue-numbers which are either placed on the border lines between selected pairs of neighbouring squares of the grid or placed after slash marks on. . . .
Factor Lines
Age 7 to 14
Challenge Level
Arrange the four number cards on the grid, according to the rules, to make a diagonal, vertical or horizontal line.
Rectangle Outline Sudoku
Age 11 to 16
Challenge Level
Each of the main diagonals of this sudoku must contain the numbers 1 to 9 and each rectangle width the numbers 1 to 4.
The Moons of Vuvv
Age 7 to 11
Challenge Level
The planet of Vuvv has seven moons. Can you work out how long it is between each super-eclipse?
Neighbours
Age 7 to 11
Challenge Level
In a square in which the houses are evenly spaced, numbers 3 and 10 are opposite each other. What is the smallest and what is the largest possible number of houses in the square?
Twin Corresponding Sudokus II
Age 11 to 16
Challenge Level
Two sudokus in one. Challenge yourself to make the necessary connections.
Code Breaker
Age 7 to 11
Challenge Level
This problem is based on a code using two different prime numbers less than 10. You'll need to multiply them together and shift the alphabet forwards by the result. Can you decipher the code?
Making Maths: Double-sided Magic Square
Age 7 to 14
Challenge Level
Make your own double-sided magic square. But can you complete both sides once you've made the pieces?
Diagonal Product Sudoku
Age 11 to 16
Challenge Level
Given the products of diagonally opposite cells - can you complete this Sudoku?
Prompt Cards
Age 7 to 11
Challenge Level
These two group activities use mathematical reasoning - one is numerical, one geometric.
Gabriel's Problem
Age 11 to 14
Challenge Level
Gabriel multiplied together some numbers and then erased them. Can you figure out where each number was?
Peaches Today, Peaches Tomorrow...
Age 11 to 14
Challenge Level
A monkey with peaches, keeps a fraction of them each day, gives the rest away, and then eats one. How long can his peaches last?
Latin Lilies
Age 7 to 16
Challenge Level
Have a go at this game which has been inspired by the Big Internet Math-Off 2019. Can you gain more columns of lily pads than your opponent?
Pole Star Sudoku 2
Age 11 to 16
Challenge Level
This Sudoku, based on differences. Using the one clue number can you find the solution?
Twinkle Twinkle
Age 7 to 14
Challenge Level
A game for 2 people. Take turns placing a counter on the star. You win when you have completed a line of 3 in your colour.
Mystery Matrix
Age 7 to 11
Challenge Level
Can you fill in this table square? The numbers 2 -12 were used to generate it with just one number used twice.
Advent Sudoku
Age 11 to 14
Challenge Level
Rather than using the numbers 1-9, this sudoku uses the nine different letters used to make the words "Advent Calendar".
Extra Challenges from Madras
Age 11 to 14
Challenge Level
A few extra challenges set by some young NRICH members.
Seven Flipped
Age 7 to 11
Challenge Level
Investigate the smallest number of moves it takes to turn these mats upside-down if you can only turn exactly three at a time.
Seasonal Twin Sudokus
Age 11 to 16
Challenge Level
This pair of linked Sudokus matches letters with numbers and hides a seasonal greeting. Can you find it?
Cinema Problem
Age 11 to 14
Challenge Level
A cinema has 100 seats. Show how it is possible to sell exactly 100 tickets and take exactly £100 if the prices are £10 for adults, 50p for pensioners and 10p for children.
Take Three Numbers
Age 7 to 11
Challenge Level
What happens when you add three numbers together? Will your answer be odd or even? How do you know?
Number Daisy
Age 11 to 14
Challenge Level
Can you find six numbers to go in the Daisy from which you can make all the numbers from 1 to a number bigger than 25?
Zargon Glasses
Age 7 to 11
Challenge Level
Zumf makes spectacles for the residents of the planet Zargon, who have either 3 eyes or 4 eyes. How many lenses will Zumf need to make all the different orders for 9 families?
Polo Square
Age 7 to 11
Challenge Level
Arrange eight of the numbers between 1 and 9 in the Polo Square below so that each side adds to the same total.
All Seated
Age 7 to 11
Challenge Level
Look carefully at the numbers. What do you notice? Can you make another square using the numbers 1 to 16, that displays the same properties?
Quadruple Sudoku
Age 11 to 16
Challenge Level
Four small numbers give the clue to the contents of the four surrounding cells.
NRICH is part of the family of activities in the Millennium Mathematics Project.