# Resource Title search

### Où Irons-nous?

##### Age 7 to 11 Challenge Level:

"Where Can We Visit" en Français

### Oblique Projection

##### Age 11 to 14 Challenge Level:

Explore the properties of oblique projection.

### Observing the Sun and the Moon

##### Age 7 to 14 Challenge Level:

How does the time of dawn and dusk vary? What about the Moon, how does that change from night to night? Is the Sun always the same? Gather data to help you explore these questions.

### Obsolete Primary Page

##### Age 5 to 11 Challenge Level:

Obsolete primary pages

### Obviously?

##### Age 14 to 18 Challenge Level:

Find the values of n for which 1^n + 8^n - 3^n - 6^n is divisible by 6.

### Octa Space

##### Age 7 to 11 Challenge Level:

In the planet system of Octa the planets are arranged in the shape of an octahedron. How many different routes could be taken to get from Planet A to Planet Zargon?

### Octa-flower

##### Age 16 to 18 Challenge Level:

Join some regular octahedra, face touching face and one vertex of each meeting at a point. How many octahedra can you fit around this point?

### Octagonal Ratio

##### Age 14 to 16 Short Challenge Level:

Can you find the ratio of the area shaded in this regular octagon to the unshaded area?

### Odd Dice

##### Age 14 to 16 Short Challenge Level:

These strange dice are rolled. What is the probability that the sum obtained is an odd number?

### Odd Differences

##### Age 14 to 16 Challenge Level:

The diagram illustrates the formula: 1 + 3 + 5 + ... + (2n - 1) = n² Use the diagram to show that any odd number is the difference of two squares.

### Odd One Out

##### Age 16 to 18 Short Challenge Level:

In this short problem, can you deduce the likely location of the odd ones out in six sets of random numbers?

### Odd Squares

##### Age 7 to 11 Challenge Level:

Think of a number, square it and subtract your starting number. Is the number you’re left with odd or even? How do the images help to explain this?

### Odd Stones

##### Age 14 to 16 Challenge Level:

On a "move" a stone is removed from two of the circles and placed in the third circle. Here are five of the ways that 27 stones could be distributed.

### Odd Tic Tac

##### Age 5 to 7 Challenge Level:

An odd version of tic tac toe

### Odd Times Even

##### Age 5 to 7 Challenge Level:

This problem looks at how one example of your choice can show something about the general structure of multiplication.

### Oddly

##### Age 7 to 11 Challenge Level:

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

### Odds and Evens

##### Age 11 to 14 Challenge Level:

Is this a fair game? How many ways are there of creating a fair game by adding odd and even numbers?

### Odds and Evens Made Fair

##### Age 14 to 16 Challenge Level:

In this follow-up to the problem Odds and Evens, we invite you to analyse a probability situation in order to find the general solution for a fair game.

### Odds and Threes

##### Age 7 to 11 Challenge Level:

A game for 2 people using a pack of cards Turn over 2 cards and try to make an odd number or a multiple of 3.

### Odds or Sixes?

##### Age 7 to 11 Challenge Level:

Use the interactivity or play this dice game yourself. How could you make it fair?

### Odds, Evens and More Evens

##### Age 11 to 14 Challenge Level:

Alison, Bernard and Charlie have been exploring sequences of odd and even numbers, which raise some intriguing questions...

### Of All the Areas

##### Age 14 to 16 Challenge Level:

Can you find a general rule for finding the areas of equilateral triangles drawn on an isometric grid?

### Off the Cuff

##### Age 11 to 14 Short Challenge Level:

Can you work out the ratio of shirt types made by a factory, if you know the ratio of button types used?

### Oh for the Mathematics of Yesteryear

##### Age 11 to 14 Challenge Level:

A garrison of 600 men has just enough bread ... but, with the news that the enemy was planning an attack... How many ounces of bread a day must each man in the garrison be allowed, to hold out 45. . . .

### Oh So Circular

##### Age 14 to 16 Short Challenge Level:

The diagram shows two circles and four equal semi-circular arcs. The area of the inner shaded circle is 1. What is the area of the outer circle?

### Oh! Harry!

##### Age 7 to 11 Challenge Level:

A group of children are using measuring cylinders but they lose the labels. Can you help relabel them?

### Oh! Hidden Inside?

##### Age 11 to 14 Challenge Level:

Find the number which has 8 divisors, such that the product of the divisors is 331776.

### OK! Now Prove It

##### Age 16 to 18 Challenge Level:

Make a conjecture about the sum of the squares of the odd positive integers. Can you prove it?

### Old Nuts

##### Age 16 to 18 Challenge Level:

In turn 4 people throw away three nuts from a pile and hide a quarter of the remainder finally leaving a multiple of 4 nuts. How many nuts were at the start?

### Old Order

##### Age 11 to 14 Short Challenge Level:

Who is the youngest in this family?

### Oldest and Youngest

##### Age 14 to 16 Short Challenge Level:

Edith had 9 children at 15 month intervals. If the oldest is now six times as old as the youngest, how old is her youngest child?

### Olympic Cards

##### Age 5 to 11 Challenge Level:

Design your own scoring system and play Trumps with these Olympic Sport cards.

### Olympic Logic

##### Age 11 to 16 Challenge Level:

Can you use your powers of logic and deduction to work out the missing information in these sporty situations?

### Olympic Magic

##### Age 14 to 16 Challenge Level:

in how many ways can you place the numbers 1, 2, 3 … 9 in the nine regions of the Olympic Emblem (5 overlapping circles) so that the amount in each ring is the same?

### Olympic Maths

##### Age 5 to 7

To celebrate the 2016 Olympic Games, why not have a go at these maths and sport challenges?

### Olympic Maths

##### Age 7 to 11

Celebrate the 2016 Olympics by having a go at these sports and maths challenges for upper primary students.

### Olympic Measurements

##### Age 7 to 16

Alan Parr offers some thoughts on various measurements recorded during the Olympic Games. From the accuracy of timing in the pool to the point system in the heptathlon, Alan gives us food for. . . .

### Olympic Measures

##### Age 11 to 14 Challenge Level:

These Olympic quantities have been jumbled up! Can you put them back together again?

### Olympic Records

##### Age 11 to 14 Challenge Level:

Can you deduce which Olympic athletics events are represented by the graphs?

Olympic Records

### Olympic Rings

##### Age 5 to 7 Challenge Level:

This problem is intended to get children to look really hard at something they will see many times in the next few months.

### Olympic Starters

##### Age 7 to 11 Challenge Level:

Look at some of the results from the Olympic Games in the past. How do you compare if you try some similar activities?

### Olympic Triathlon

##### Age 14 to 16 Challenge Level:

Is it the fastest swimmer, the fastest runner or the fastest cyclist who wins the Olympic Triathlon?

### Olympic Turns

##### Age 7 to 11 Challenge Level:

This task looks at the different turns involved in different Olympic sports as a way of exploring the mathematics of turns and angles.

### On Problems and Problem Solving - Looking Backward and Forward

##### Age 5 to 18

Jenny Piggott reflects on the event held to mark her retirement from the directorship of NRICH, but also on problem solving itself.

### On Target

##### Age 7 to 11 Challenge Level:

You have 5 darts and your target score is 44. How many different ways could you score 44?

### On the Edge

##### Age 11 to 14 Challenge Level:

If you move the tiles around, can you make squares with different coloured edges?

### On the Edge Poster

##### Age 11 to 14 Challenge Level:

On the Edge Poster - June 2010

### On the Importance of Pedantry

##### Age 16 to 18

A introduction to how patterns can be deceiving, and what is and is not a proof.