Who said that adding couldn't be fun?
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?
The letters in the following addition sum represent the digits 1 ... 9. If A=3 and D=2, what number is represented by "CAYLEY"?
Can you substitute numbers for the letters in these sums?
This article, written for teachers, looks at the different kinds of recordings encountered in Primary Mathematics lessons and the importance of not jumping to conclusions!
Some Games That May Be Nice or Nasty for an adult and child. Use your knowledge of place value to beat your opponent.
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.
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.
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.
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?
How many more miles must the car travel before the numbers on the milometer and the trip meter contain the same digits in the same order?
Replace each letter with a digit to make this addition correct.
Think of a two digit number, reverse the digits, and add the numbers together. Something special happens...
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. . . .
Choose four different digits from 1-9 and put one in each box so that the resulting four two-digit numbers add to a total of 100.
Dicey Operations for an adult and child. Can you get close to 1000 than your partner?
A three digit number abc is always divisible by 7 when 2a+3b+c is divisible by 7. Why?
This 100 square jigsaw is written in code. It starts with 1 and ends with 100. Can you build it up?
How many solutions can you find to this sum? Each of the different letters stands for a different number.
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.
What do the digits in the number fifteen add up to? How many other numbers have digits with the same total but no zeros?
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. . . .
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.
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)?
Number problems at primary level that require careful consideration.
Find the values of the nine letters in the sum: FOOT + BALL = GAME
Find the sum of all three-digit numbers each of whose digits is odd.
What happens when you round these numbers to the nearest whole number?
What happens when you round these three-digit numbers to the nearest 100?
Can you work out some different ways to balance this equation?
Use two dice to generate two numbers with one decimal place. What happens when you round these numbers to the nearest whole number?
Can you replace the letters with numbers? Is there only one solution in each case?
In this 100 square, look at the green square which contains the numbers 2, 3, 12 and 13. What is the sum of the numbers that are diagonally opposite each other? What do you notice?
Number problems at primary level to work on with others.
Three people chose this as a favourite problem. It is the sort of problem that needs thinking time - but once the connection is made it gives access to many similar ideas.
Number problems at primary level that may require resilience.
Number problems for inquiring primary learners.
Can you complete this calculation by filling in the missing numbers? In how many different ways can you do it?
Powers of numbers behave in surprising ways. Take a look at some of these and try to explain why they are true.
Using balancing scales what is the least number of weights needed to weigh all integer masses from 1 to 1000? Placing some of the weights in the same pan as the object how many are needed?
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?
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?
In the multiplication calculation, some of the digits have been replaced by letters and others by asterisks. Can you reconstruct the original multiplication?
The number 3723(in base 10) is written as 123 in another base. What is that base?
This multiplication uses each of the digits 0 - 9 once and once only. Using the information given, can you replace the stars in the calculation with figures?
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.
How many positive integers less than or equal to 4000 can be written down without using the digits 7, 8 or 9?
How many six digit numbers are there which DO NOT contain a 5?
Follow the clues to find the mystery number.
Take any four digit number. Move the first digit to the 'back of the queue' and move the rest along. Now add your two numbers. What properties do your answers always have?